Dissertations / Theses: 'Glass lasers'

1

Hofmann, Peter. "Monolithic Soft Glass Single Frequency Fiber Lasers." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/268515.

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Envisioning novel fully monolithic fiber-optical devices, this dissertation investigates four fiber optical devices both, active and passive, that contribute to the goal of further integrating and miniaturizing fiber optics. An all phosphate glass fiber laser was designed in an effort to reduce laser intensity noise by reducing cavity losses and low mechanical strength that arise from intra-cavity fusion splices between silica fiber Bragg gratings (FBG) and phosphate active fiber in state of the art phosphate single frequency fiber lasers. Novel phosphate glass based FBGs have been fabricated utilizing high intensity laser pulses at 193 nm and a phase-mask. Net reflectivities of up to 70 % and a bandwidth of 50 pm have been achieved in the FBGs. The laser design comprised two of the novel FBGs and a short section of Er³⁺Yb³⁺ phosphate fiber to form a distributed Bragg reflector (DBR) laser. The performance of the new laser has been compared to a conventional phosphate fiber laser. Particular focus was put on the laser intensity noise due to its dependence on intra-cavity losses. Relative intensity noise (RIN) amplitudes of -80 dB/Hz have been measured for both lasers when operating at comparable output powers. For similar levels of absorbed pump power the relaxation oscillation frequencies (ROF) were shifted towards lower frequencies in the new laser. ExcessFBG scattering losses and mode-field miss-match between the active and passive fiber limited the output power of the new laser to 16 mW compared to 140 mW in the conventional laser. A monolithic all-phosphate glass fiber laser with up to 550 mW output power that is operating at a single longitudinal mode and exhibiting narrow linewidth is presented. The laser cavity has been formed by inscribing FBGs directly into heavily Er³⁺Yb³⁺ doped phosphate glass fiber using femtosecond laser pulses and a phase mask, completely eliminating the need for intra-cavity fusion splices. A linewidth of less than 60 kHz and relaxation oscillation peak amplitudes below -100 dB/Hz without active suppression of RIN have been measured. The compact form factor and higher output power combined with the low noise and narrow linewidth characteristic make this laser an ideal candidate for ranging, interferometry and sensing applications. Strong and robust Bragg gratings in optical fiber fabricated from highly photosensitive photo-thermo-refractive (PTR) glass are demonstrated. The fibers were drawn at 900 °C from a machined PTR-glass preform. A low power two beam interference pattern from a continuous wave (cw) He-Cd laser with a wavelength of 325 nm was used to write gratings into the fibers, achieving peak grating strengths of 20 dB and a spectral width of 45 pm. The gratings showed no sign of degradation when exposed to a high temperature environment of 425 °C for several hours. This is significantly higher when compared to standard Telecom FBGs which are rated for operation temperatures below 200 °C. A detailed study of novel mode-field adapters (MFA) based on multi-mode interference in graded index multi-mode fibers (GIMF) is presented. MFAs are often used in cases when low coupling losses between single mode fibers with very different mode-field diameters are needed. Here a new type of MFAs has been fabricated and characterized from a selection of commercially available single mode and graded index fibers. Compared to existing techniques the presented MFAs can be fabricated very quickly and are not limited to certain fiber types. Insertion losses of 0:5 dB over a spectral range of several hundred nm have been obtained with an ultra compact MFA with a length of 275 μm.

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Mwarania, Eustace Kaburu. "Planar ion-exchanged waveguide lasers in glass." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/399434/.

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This thesis describes the realisation of integrated optical sources in rare-earth doped glass substrates using ion-exchange planar waveguide fabrication technology. The planar configuration offers the possibility of photolithographic definition of complex multiple-cavity devices, of monolithic integration of devices such as modulators for switching and tuning, and for mass production. A process to introduce rare-earth ions into ion-exchangeable glasses was developed, and used to fabricate neodymium-doped BK-7 glass substrates. Techniques for design, fabrication and characterisation of potassium ion-exchanged waveguides for laser applications in these substrates are described. The properties of waveguides in a substrate doped with 1.5wt.% neodymium oxide are presented. A method to form laser resonators incorporating ion-exchanged waveguides is described. Single- and multiple-cavity waveguide lasers operating in single transverse mode at both pump and lasing wavelengths have been demonstrated and their characteristics are presented. The factors affecting lasing thresholds of the single-cavity lasers were investigated, and devices with thresholds low enough to be pumped by a single-stripe laser diode were realised. A theoretical model for the analysis of optical multiple-cavity resonators is developed. These resonators are shown to exhibit frequency selecting properties that may be exploited to realise multifunctional sources. The potential of the planar configuration was demonstrated by integrating Y-junction multiple-cavity waveguide lasers and monolithic thermo-optic phase modulators. These lasers have been line-narrowed, tuned in wavelength, and Q-switched by applying modulation voltages to the thermo-optic modulators.

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3

Peng, Xiang. "Erbium-doped tellurite glass microsphere amplifiers and lasers." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280529.

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Due to the properties of extremely high quality factor and small mode volume, microsphere resonators have attracted considerable attention for signal processing, fiber communication and photon computation applications. This research work studies the optical properties of microsphere amplifier and laser. The Er³⁺-doped tellurite glass was examined, including emission cross-section, absorption cross-section and lifetime analysis. McCumber and Judd-Ofelt theories were used for theoretical calculations. Whispering gallery modes in the microsphere were calculated by using the measured parameters. Signal enhancement was obtained in this Er³⁺-doped tellurite glass microsphere. The enhancement of this Er³⁺-doped tellurite glass microsphere exceeds 12dB. Besides, the mode in a single mode tapered fiber was analyzed. Theoretical analysis was also performed to optimize the coupling scheme. We also analyzed the lasing characteristics of microsphere laser, including threshold, lasing wavelength, output power optimization, and temperature dependence. Theoretical calculations for these properties were also presented. State-of-the-art L-band microsphere laser with maximum output power of 124.5 μW was demonstrated which has potential in various photonic applications.

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Ohtsuki, Tomoko 1960. "Rare-earth-doped glass waveguides for amplifiers and lasers." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282169.

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Several different glass materials were investigated for waveguide amplifier and laser applications, and the potential to realize practical devices with these materials were examined using waveguides fabricated by ion exchange processes. Channel waveguides in an erbium doped phosphate laser glass were fabricated by a dry silver-film ion exchange technique, and the effects of high Er³⁺ concentration were investigated in terms of Er³⁺ ion interactions and energy transfer from Yb³⁺ to Er³⁺. Cooperative upconversion coefficients of the ⁴I₁₃/₂ level,7.7±0.7x 10⁻¹⁹ cm³/sec and 9.3±0.7x10⁻¹⁹ cm³/sec, were obtained experimentally for Er³⁺ concentration of 1x10²⁰ cm³ in the bulk and waveguide samples, respectively. These values are one order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er³⁺ concentration was found to be small. The effects of cooperative upconversion on the gain performance were analyzed for different Er³⁺ concentrations using a theoretical model which adopted experimentally obtained parameters. Given the small cooperative upconversion coefficients in this glass, Er³⁺ concentrations potentially as high as 3.7x10²⁰ cm⁻³ were shown to be feasible by the modeling. This would result in a 12 dB gain with a 4 cm long waveguide for 150 mW pump power at 1.48 μm. The transfer efficiency from Yb3+ to Er³⁺ was found to be 95% or higher for samples with Er³⁺ concentrations of 1.9x10²⁰ cm⁻³, and 24x10²⁰ cm⁻³, even when the ratio of the concentrations, Yb/Er, is only about 1.2 and 2. Planar channel waveguides of rare-earth doped fluoride glass were demonstrated with single mode excitation and propagation loss below 3 dB/cm. The waveguide core was fabricated by Ag⁺-Na⁺ molten salt ion exchange process in a borosilicate glass (BGG31), and a Nd³⁺-doped ZBLAN glass was used as a cladding. A 0.45 dB signal amplification at 1.064 μm was observed in the fabricated 1cm long waveguide, and a 0.9 dB amplification is expected at the emission peak (1.049 μm). Modeling results suggest that 2.5 dB/cm is possible by improving surface flatness of the ZBLAN glass.

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Richards, Billy Donald Orac. "Tellurite glass mid-infrared (1.9 - 2.1 um) fibre lasers." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493606.

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Tellurite glass has certain material properties which overcome some of the drawbacks of other established fibre laser host glasses such as silica, fluoride and germanate fibre. For this reason, developing fibre lasers using tellurite fibre is of interest for applications such as light detection and ranging (lidar), sensing and medicine.

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Haythornthwaite, Charles Richard. "Spectroscopy of chromium doped glass for amplifiers and lasers." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/351503/.

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To date, there has been no demonstration of a transition metal laser that uses a glass host. Calculations show that if reasonable pump power could be confined to the small cross-sectional area of a fibre optic core, the threshold pump power could be brought down to a realistic level for laser action. A transition metal fibre laser, if practicable, would make a cheap, compact and highly tunable laser source in the near infrared. This project comprised two parts. Firstly, spectroscopy and developmental work on a host glass identified as being an excellent prospect for a Cr3+ fibre laser. Secondly, the spectroscopic investigation of a new family of glass found to host Cr4+. Lithium lime silicate (LLS) glass was identified as an excellent prospect for a Cr3+ fibre laser. Not only possessing suitable thermal properties for fibre drawing, LLS had a radiative quantum efficiency (QE) measured as 15% - a very high figure for Cr3+ doped glass. It absorbed in two broad bands, 400-500nm and 600-750nm and the emission spectrum was also extremely broad, extending between 700nm and 1050μm. The upper state lifetime was about 35 μs and the peak cross-section of emission was found to be 6 x 10−21cm2. The LLS composition was optimised in terms of its spectroscopy and thermal properties and a fibre was fabricated. An excited state absorption (ESA) investigation was performed on the fibre - this is believed to be the first report of an ESA experiment on transition metal doped glass. Unfortunately, the fibre quality was not sufficient to make a realistic attempt at a demonstration of a fibre laser. There are very few glasses known to host Cr4+, and none of these have thermal properties suitable for fibre drawing. This thesis reports the discovery that sulphide chalcogenide glasses, which are stable enough for fibre drawing, also host the chromium (IV) ion. A wide range of sulphide based glass was fabricated and the spectroscopic investigation revealed the QE to be low, ranging from 0 to 3%. The absorption spectra typically extended between 600nm and 1300nm and the emission between 0.8μm and 1.5μm. As the samples were warmed up from liquid nitrogen to room temperature, the peak of emission experienced a remarkable blue shift of up to 400nm owing to a site-dependent non-radiative decay mechanism. The upper state lifetime was found to be about 1 μs. Despite the low QE and short lifetime, calculations suggest that laser action in a low-loss narrow-cored fibre might still be feasible. However, the lifetime cross-section product for arsenic trisulphide, the best of the glasses tried, was about a factor of six times smaller than the Cr3+ doped LLS.

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Zheng, Liyun. "Process control of applied laser system for enhanced glass production." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1718.

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Thesis (Ph. D.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xiv, 195 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 172-177).

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Fusari, Flavio. "Continuous wave and modelocked femtosecond novel bulk glass lasers operating around 2000 nm." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1694.

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This thesis reports on the development of glass-based femtosecond laser sources around 2 µm wavelength. In order to be able to produce 2 µm radiation the dopants used were trivalent Thulium (Tm³⁺) and trivalent Holmium (Ho³⁺) that could be optically pumped with Ti:Sapphire radiation at 0.8 µm and semiconductor disk lasers (SDL) at 1.2 µm. The samples were produced at Leeds University and polished in-house in bulk form and deployed in free space laser cavities. Tellurite compounds doped with Tm³⁺ produced stable continuous wave 1.94 µm radiation when pumped at 800 nm with a maximum efficiency of 28.4% with respect to the absorbed power and maximum output power around 120 mW when pumped using a Ti:Sapphire operating around 0.8 µm. The radiation was broadly tunable across 130 nm. Tm³⁺-Ho³⁺ doubly doped tellurite samples lased around 2.02 µm with maximum efficiency of 25.9% and with P[subscript(OUT)]=75 mW and a smooth tunability of 125 nm. The fluorogermanate glass doped with Tm³⁺ gave an absorbed to output power efficiency of 50%. The maximum continuous wave output powers obtained were around 190 mW and limited by the available pump power at 0.8 µm. These results together with a very low threshold of 60 mW of incident power were comparable to the crystalline counterparts to this gain medium. The Tm3+ tellurite and the Tm³⁺-Ho³⁺ tellurite compounds were also pumped by an SDL operating at 1215 nm to obtain an indication of the viability of such a pump scheme. The results were a maximum internal slope efficiency of 22.4% with a highest output power of 60 mW. The comparison demonstrated that 1.2 µm pumping was competitive with using 0.8 µm wavelength. The use of semiconductor saturable absorbing mirror (SESAM) technology was used for the modelocking of these lasers. The SESAM was produced in Canada and implanted with As⁺ ions in order to reduce the relaxation time. Trains of transform-limited laser pulses at 222 MHz as short as 410 fs centred at 1.99 µm were produced for the first time with a bulk Tm³⁺:Fluorogermanate glass. The maximum average output power obtained was of 84 mW. The same SESAM deployed on the Tm³⁺-Ho³⁺ Tellurite compounds gave trains of transform-limited pulses as short as 630 fs at 2.01 µm with a repetition rate of 143 MHz and a maximum averaged output power of 43 mW. The regime of propagation obtained was soliton-like and the modelocking was self-starting. The results obtained with bulk glass were very promising and open interesting research pathways within the realm of amorphous bulk gain media.

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Mairaj, Arshad Khawar. "Optical waveguides and lasers in improved gallium lanthanum sulphide glass." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15476/.

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A number of developmental stages are still required to advance and mature optical waveguide technology in non-silica glasses. The primary stage includes raw material purification and improving quality and thermal stability of an optical glass for waveguide fabrication processes. Further stages can include design, application and integration of these waveguides with other photonic devices. Gallium lanthanum sulphide (Ga:La:S) chalcogenide glass (ChG), first discovered in 1976, is a material proposed as an optical waveguide for use in the infrared (IR). Interest in this glass system has been maintained, over the years, primarily due to its exceptional and unusual optical properties. The aim of this project is to advance the current state of art for Ga:La:S glass by demonstrating working solutions for fibre and planar waveguides. Chapter 1 of this thesis provides a general overview of current glass technology and the motivations of this project. The optical glass system under study has yet to attain acceptable stability for fibre production and as such investigation into fundamental manufacturing steps is still required. Raw material purity is an important aspect, of fabricating practical optical glasses, and directly affects performance. Chapter 2 of this thesis describes the purification and synthesis processes performed to produce raw materials with purity far superior to similar products available commercially. Each powdered precursor synthesised in our labs and used in fabrication of Ga:La:S based optical glasses has a transition metal impurity content of less than 1 parts-per-million (ppm wt%). The water content, OH-, of these fabricated glasses has been reduced to < 2 ppm. The primary concern when fabricating Ga:La:S based optical fibre is crystallisation. Optimising the composition to obtain a glass suitable for fibre fabrication is significant in providing thermal stability for fibre drawing. Chapter 3 describes some of the steps taken towards the fabrication and improvement of Ga:La:S based glasses for waveguide technology. The invention of a new variant in the Ga:La:S family of glasses provides key enhancements over existing Ga:La:S and Ga:La:S:O glasses. The hybrid oxy-chalcohalide glass, Ga:La:S:O:F, contains compounds of sulphide, oxide and fluoride as constituents. This new glass type provides significant thermal stability, in the context of fibre drawing. Fibre drawn from a single piece of polished Ga:La:S:O:F glass had attenuation at 1.5 and 4.0 µm of 3.3 and 2.1 dB m-1 respectively. The reduction of the OH- absorption at 2.9 µm to < 1 ppm in Ga:La:S:O:F glass, can potentially allow development of planar waveguide devices for the mid-IR. A range of extremely stable compositions for Ga:La:S, Ga:La:S:O and Ga:La:S:O:F glasses was also identified. These glasses were amorphous upon slow cooling in the furnace (8 oC min-1) indicating danced thermal stability against crystallisation. In Chapter 4 and 5, the fabrication and characterisation of channel waveguides is discussed. Photoinduced changes were introduced by directly writing waveguides into Ga:La:S glass through exposure to short wavelength light (l = 244 nm). Focused fluence of 1.5 - 150 J/cm2 from a continuous wave laser operating at 244 mn was applied, inducing photocompaction and photochemical changes. These passive channel waveguides were spatially single-mode and bad Dn ~ +10-3. The first chalcogenide channel waveguide laser in Nd3+-Ga:La:S glass was also demonstrated. Maximum laser output (l = 1075 nm) of 8.6 mW for an absorbed laser pump power of 89 mW and slope efficiency of 17% was achieved with measured device attenuation of < 0.5 dB cm-1. Discussed in Chapter 6 is the first demonstration of the hotdip spin coating process used to fabricate thin films of a ChG (Ga:La:S). This promising technique is presented as an enhancement to waveguide development. In addition, buried (50 µm) channel waveguides were directly written into the spun thin film using a pulsed laser source (l = 830 nm). These buried channel waveguides had a measured attenuation of < 1 dB cm-1.

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Panitchob, Yuwapat. "Integration of glass microspheres and planar waveguides for microsphere lasers." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/69881/.

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Microsphere resonators with sizes in the micrometer range are reported to support very high Q’s of more than 109 for a fused silica microsphere. This high Q value represents many promising characteristics such as low cavity loss, long cavity life time, and narrow band width. With their remarkable characteristics, microsphere resonators can be used in various applications such as the narrow band filter, add-drop multiplexer, microlasers, and etc. In this work, the integration of microspheres with planar waveguides is the main focus. High quality neodymium-doped BK7 microspheres are fabricated and characterised to observe laser oscillation at 1.06 μm from the 4F3/2 - 4I11/2 transition. Theoretical calculation of the microsphere mode and field and the characteristic equation which describes the relation of the sphere mode numbers l, m, n to the wavelength, are obtained. The theoretical expressions of the microsphere WGM can be described with the sphere mode numbers based on spherical Bessel and Hankel functions. Coupling and quality factors of the waveguide-coupled system are obtained by integrating the overlapped fields of the microsphere and waveguide, and the study of Q factors as a function of sphere/waveguide separation are elaborated. Theoretical models to calculate the total loss and gain of the microsphere lasers and the Q which is required for lasing action, are developed. The expressions for power threshold in the microsphere and in the input waveguide are derived, and the threshold pump power as a function of sphere/waveguide separation is obtained. Experimental work to observe the WGM propagation of a passive microsphere has been carried out, and results obtained at wavelengths in the 800 nm and 1550 nm regions, and modal assignment including the evaluation of Q for each system are carried out. The experiments to observe the fluorescence and the lasing oscillation of the neodymium-doped BK7 microspheres are demonstrated. The measurement of the fluorescence lifetime of a neodymium-doped BK7 microsphere, is obtained. A laser oscillation is demonstrated with the free-space pump excitation, with the threshold pump power of 8 mW at λ = 808nm.

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11

Mackechnie, Colin Jardine. "An investigation into thulium and ytterbium doped glass fibre lasers." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/399144/.

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The work described in this thesis is the result of three years of study in thulium and ytterbium doped glass optical fibres with a view to investigating and characterising laser action in these media. In particular an investigation has been carried out into the effect that pump excited state absorption (ESA) has on the 1064nm-pumped Thulium-doped silica 2µm fibre laser, resulting in the first measurement, in terms of cross section, of the ESA from the 3H4 level in the 1-1.5µm region for Tm:silica. Laser oscillation has been observed at ~1.9µm in Tm-doped lead germanate fibre pumped at ~790nm. This new glass fibre was specially developed to have an appropriate phonon energy to enhance the lasing properties of this thulium transition over that in silica or fluoride hosts. It is the first glass fibre laser based on a germanate glass. The lowest ever recorded threshold for this transition in any glass has been recorded at 3.6mW of launched power. In order to investigate infra-red pumped visible upconversion lasers in Tm:ZBLAN fibre, ytterbium doped silica fibre lasers were first studied as a route to producing the required pump wavelengths. By using a novel pumping scheme in the wing of the absorption band at 1064nm or 1047nm, efficient laser action achieved in the long wavelength range of the emission, between 1096nm and 1180nm. The lowest recorded threshold was 17mW and the highest measured slope efficiency was 87% (both with respect to launched power). These investigations confirm the versatility of Yb:silica fibre lasers. With the successful development of the Yb:silica fibre laser operating at the required pump wavelength, an investigation was carried out into single-wavelength-pumped, room temperature upconversion in thulium-doped ZBLAN with the aim of producing a blue laser. Blue lasing was observed in the range 476nm - 486nm (the longest and shortest laser wavelengths recorded for this transition) with pump wavelengths between 1100nm and 1141nm (the longest and shortest pump wavelengths reported). The lowest threshold was measured as 11mW (launched power)and the maximum slope efficiency was 23% (with respect to launched power), results which indicate potential for an infra-red diode pumped blue laser.

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12

Li, Li. "Extremely Compact High-Power Er3+-Yb3+-Codoped Phosphate Glass Fiber Lasers." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/193824.

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Extremely compact high-power fiber lasers operating at eye-safe telecom wavelength of 1.5 μm have been achieved by systematic experimental studies. Heavily Er3+-Yb3+-codoped phosphate glasses have been chosen as the host glass for our fibers and 1.5 μm lasers have been realized when pumped with 975 nm laser diodes.The first short-length cladding-pumped fiber laser with watt-level CW output power has been demonstrated by an 11-cm-long doped step-index phosphate fiber. Without active cooling, 1.5 W output power at 1535 nm has been obtained.Thermoelectric cooler has been used for heavily doped phosphate step-index fibers. A dual-end-pumped actively cooled fiber laser has generated more than 11 W CW output power at 1535 nm from an 11.9 cm long active fiber. A fully 3-dimensional thermal analysis has been performed to calculate the internal temperature distribution of the short-length fiber laser and the simulated results have been experimentally verified.Phosphate glass microstructured optical fibers (MOFs) with large active cores have been fabricated. The first demonstrated short phosphate MOF laser has generated > 3 W single-mode CW output power from an 11-cm-long fiber. The impacts of depressed-core-index and annealing upon MOF's modal property have been systematically investigated. Extremely compact high-power fiber laser is demonstrated by a heavily doped MOF laser and > 4.5 W single-mode CW output power is delivered from a 3.5 cm long fiber. Finally, a high-power single-frequency fiber laser is realized by splicing a FBG with a 3.8 cm long MOF, which achieves > 2 W single-frequency output power.

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Pugh, Andrew. "Elemental analysis of glass optical fibres with high spatial resolution." Thesis, Sheffield Hallam University, 1991. http://shura.shu.ac.uk/20251/.

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The properties of glass optical fibres are very strongly dependent on the elemental concentration profiles of the fibre cores. Core dopants such as germanium define the core refractive index, which in turn defines the manner in which the light is transmitted through the fibre. Erbium in fibre cores can facilitate the operation of fibre lasers and aluminium in turn can control the erbium distribution. The aim of the project described in this thesis was to measure the elemental concentration profiles in a variety of fibre cores using X-ray microanalysis in an electron microscope. Conventional X-ray microanalysis of bulk samples has an analytical resolution in the order of a micron. With monomode optical fibre cores having cores typically three microns in diameter the resolution of the conventional technique is plainly inadequate. An experimental technique has been developed for the preparation of thin cross-sectional samples of glass optical fibres. Application of this technique has facilitated the preparation and analysis of thin film specimens with an average thickness of 400 microns. This approach has allowed analysis to be performed with an effective spatial resolution of 100-300 nm. The technique has been applied to the determination of germanium concentration in Raman fibres, to the investigation of erbium confinement in erbium doped fibres and to the investigation of inter-ionic diffusion in semiconductor doped fibres. It has been shown that the germanium, and hence refractive index, profile of germanium doped fibres is not changed by the process of fibre drawing. Evidence has been gathered supporting the theory of erbium confinement by aluminium and an important degree of elemental diffusion has been shown to take place during the drawing of semiconductor doped fibres. In addition an experimental technique has been developed for the preparation of thin cross-sectional samples of glass optical fibres.

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Thompson, Christopher E. "Development of system parameters for enhanced cutting and finishing of handglass using a CO₂ laser." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1448.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains x, 65 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 61).

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15

Kim, Min-Young. "Delay induced instabilities in coupled semiconductor lasers and Mackey-Glass electronic circuits." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2722.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Andrusyak, Oleksiy G. Glebov Leonid B. "Dense spectral beam combining with volume bragg gratings in photo-thermo-refractive glass." S. l. : S. l. : Bordeaux 1 ; University of Central Florida Orlando, Florida, 2009. http://ori-oai.u-bordeaux1.fr/pdf/2009/ANDRUSYAK_OLEKSIY_2009.pdf.

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Andrusyak, Oleksiy. "DENSE SPECTRAL BEAM COMBINING WITH VOLUME BRAGG GRATINGS IN PHOTO-THERMO-REFRACTIVE GLASS." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2808.

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Beam combining techniques have become an important tool in the design of high-power high-brightness laser systems. Spectral beam combining (SBC) is an incoherent combining technique that does not require phase control of sources, allowing for a stable and robust system. Using SBC, beams from an array of lasers with each element operated at a different wavelength are combined into a single near-diffraction-limited beam with the same aperture using dispersive optical elements. SBC by means of volume Bragg gratings (VBGs) utilizes unique spectral response of VBGs: diffraction efficiency is close to unity when the Bragg condition is satisfied and is close to zero at multiple points corresponding to particular wavelength offsets from Bragg condition. High-efficiency VBGs can be recorded in UV-sensitive photo-thermo-refractive (PTR) glass. Narrow-band reflecting VBGs allow multi-channel SBC with high spectral density of channels. In this dissertation, experimental results of SBC with high spectral density of combined channels in two spectral regions of interest (1064 and 1550 nm) are reported. The behavior of narrow-band VBGs under high-power laser radiation is investigated. A laser system with kW-level output power and near-diffraction-limited divergence of spectrally-combined output beam is demonstrated. The system combines five randomly-polarized Yb-doped fiber lasers with 0.5 nm spectral separation in central wavelengths using narrow-band reflecting VBGs with absolute efficiency of combining > 90%. A novel design of a multi-channel high-power SBC system is suggested. In this approach, a common-cavity is created for all channels such that wavelengths of the sources are passively controlled by the combination of a common output coupler and intra-cavity VBGs which also act as combining elements. Laser wavelengths are automatically selected to match resonant wavelengths of respective VBGs. We report successful demonstration of a passively-controlled SBC system consisting of two amplifiers in a common cavity configuration. A compact and rugged monolithic SBC module based on multiplexed VBGs is introduced. Experimental results of a four-channel implementation of such module are discussed. Modular design of high-power laser systems is suggested with multiple modules arranged in a series. We show that with basic combining parameters achieved up to date, laser systems with 10 kW output power can be constructed using this arrangement. Further scaling to 100 kW power level is discussed.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD

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Shaukat, Saleem Farooq. "Optical and bulk physical characteristics of heavy metal fluoride glass scintillators containing cerium." Thesis, Brunel University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362404.

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Lauder, Richard David Templeton. "An investigation into optical amplifiers and upconversion lasers using rare earth doped fluorozirconate glass fibre." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/399118/.

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This thesis presents the results of a three year study into the use of trivalent rare-earth doped fluorozirconate fibre for potential diode-pumped amplifiers and upconversion lasers. A diode-pumped, high-gain, thulium-doped, fluoride-fibre optical amplifier around 0.8µm, for use in the first optical communications window, is reported. Using only one 100mW single stripe diode laser as the pump source for this first window optical amplifier, small-signal gains in excess of 20dB are reported for input signals of -10 dBm tunable from 801nm to 810nm. The noise figure for this amplifier was around 5 to 6dB, limited by back-reflected amplified spontaneous emission caused by the detection technique. Without this the noise figure would be below 4dB. The amplification of Q-switched AlGaAs diode lasers to high power using a similar thulium-doped fibre amplifier is also described. Peak powers of 12.5W useable output were observed. The pulses were 15ps long and amplified at a repetition rate of 7MHz using one 100mW single-stripe diode laser as the pump source. Thulium and praseodymium doped fluorozirconate fibres have also been investigated as possible infrared-pumped, visible upconversion lasers. Blue lasing using a praseodymium doped fibre has been optimised, while various spectroscopic measurements have been made of possible thulium upconversion systems.

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SHIBUYA, ELISA K. "Acoplamento laser - espectrometro de massa de dupla focalizacao com fonte de plasma induzido (LA-HR-ICPMS): estudos fundamentais e analises quantitativa em amostras solidas." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9279.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:97/09917-0

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RIQUELME, PINCHEIRA Pablo Isaias. "Theoretical and experimental study of the lévy statistics and photonic spin glass phase in random lasers." Universidade Federal de Pernambuco, 2017. https://repositorio.ufpe.br/handle/123456789/25654.

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RIQUELME PINCHEIRA, Pablo Isaias, também é conhecido em citações bibliográficas por: PINCHEIRA, Pablo Isaias Riquelme
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Since Albert Einstein established the foundations for stimulated emission of radiation in 1916, he paved a long road that culminated in the beginning of the 1960s with the invention of the laser. In a conventional laser avoiding losses by light scattering is very important. However, this paradigm is broken by the theoretical proposal of Letokhov in 1968, which says that in a disordered with gain, the scattering of light plays a positive role increasing the dwell time of light in an active medium, thereby increasing the laser amplification. Due to the disordered nature of the materials used was adopted the name Random Lasers (RLs). Random lasers have taken a new boom because they have recently been exploited as a photonic platform for studies of complex systems. This thesis covers this interdisciplinary approach that opens important new avenues for understanding the behavior of random lasers. We recently studied the intensity fluctuations in the emission of Random lasers, finding the existence of non-Gaussian statistics in these emissions behaving with Lévy-type statistics. On the other hand, in another set of theoretical and experimental work, the glassy behavior of random lasers was studied by other authors, which led to the recent experimental demonstration of symmetry replica breaking phase transition. The investigations mentioned above were taken separately, and in this work shows that these two phenomena are connected. In the first chapter we study the most important concepts of a conventional laser that are necessary to understand the random lasers. In the second chapter, we present the random lasers. We begin with the presentation of the main features of random lasers. Then, we present a connection between the phenomenon of speckle and random lasers where Speckle Contrast is used to demonstrate the multimodal nature of random lasers. This feature is applied to determine the number of modes in a random fiber laser. At the end of this chapter a work is presented where it is demonstrated for the first time Bichromatic random laser in a NdAl₃ (BO₃)₄ crystalline powder. This observation opens an avenue for random lasers applications, and, as a proof of concept, we demonstrate an optical thermometer owing to the thermal dependence of the RL emissions. The third chapter is dedicated to studying the fundamental concepts of complex systems, to understand the glassy behavior of light in random lasers. In chapter 4 essential rudiments are also given to understand Lévy statistics. In chapter 5 we show a work where we use employ the NdY BO random laser system to show that from a single set of measurement the physical origin of the complex correspondence between the Lévy fluctuation regime and the replica symmetry breaking transition to spin glass phase occurs. In chapter 6 shows the observation of replica symmetry breaking phase transition in a solution of Rhodamine and particles of TᵢO₂, where specially designed amorphous TᵢO₂ particles were synthesized to obtain identical copies of the system.
Desde que Albert Einstein estabeleceu as bases para a emissão estimulada da radiação em 1916, ele pavimentou uma longa estrada que culminou, no começo dos anos 1960, com a invenção do laser. Em um laser convencional, evitar perdas por espalhamento de luz é muito importante. No entanto, este paradigma é quebrado pela proposta teórica de Letokhov em 1968, que diz que em um meio desordenado com ganho, o espalhamento da luz desempenha um papel positivo aumentando a amplificação do laser. Devido à natureza desordenada dos materiais utilizados foi adotado o nome Random Lasers (RLs). Os lasers aleatórios tomaram um novo impulso porque foram explorados recentemente como uma plataforma fotônica para estudos de sistemas complexos. Esta tese estuda esta abordagem interdisciplinar que abre novas e importantes vias para a compreensão do comportamento de lasers aleatórios. Recentemente estudamos as flutuações de intensidade na emissão de lasers aleatórios, encontrando a existência de estatísticas não gaussianas nessas emissões que se comportam como estatísticas tipo Lévy. Por outro lado, em outro conjunto de trabalhos teóricos e experimentais, o comportamento tipo vidro de spin de lasers aleatórios foi estudado por outros autores, o que levou à recente demonstração experimental de transição de fase com quebra de simetria de réplica. As investigações mencionadas acima foram realizadas separadamente, e neste trabalho mostramos que esses dois fenômenos estão conectados. No primeiro capítulo estudamos os conceitos mais importantes de um laser convencional que são necessários para entender os lasers aleatórios. No segundo capítulo, apresentamos os lasers aleatórios. Começamos com a apresentação das principais características de lasers aleatórios. Em seguida, apresentamos uma conexão entre o fenômeno de speckle e lasers aleatórios onde Speckle Contrast é usado para demonstrar a natureza multimodal de lasers aleatórios. Esta característica é aplicada para determinar o número de modos de um laser aleatório de fibra. No final deste capítulo é apresentado um trabalho onde é demonstrado pela primeira vez o laser aleatório bicromático em um pó cristalino NdAl₃ (BO₃)₄. Esta observação abre caminho para aplicações lasers aleatórios e, como prova deste conceito, demonstramos um termômetro óptico devido à dependência térmica das emissões de RL. O terceiro capítulo é dedicado a estudar os conceitos fundamentais de sistemas complexos, para entender o comportamento tipo vidro de spin da luz em lasers aleatórios. No capítulo quatro, rudimentos essenciais também são descritos para entender as estatísticas de Lévy. No capítulo cinco mostramos um trabalho onde usamos o sistema de laser aleatório NdY BO para mostrar que a partir de um único conjunto de medições ocorre a origem física da correspondência complexa entre o regime de flutuação de Lévy e a transição de simetria de réplicas para a fase de vidro de spin. No capítulo seis, observa-se a transição de fase de ruptura de simetria de réplicas em uma solução de Rhodamine e partículas de TᵢO₂, onde se sintetizaram partículas de TᵢO₂ amorfas especialmente projetadas para obter cópias idênticas do sistema.

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Drachenberg, Derrek. "Ultra high density spectral beam combining by thermal tuning of volume Bragg gratings in photo-thermo-refractive glass." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4758.

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High power lasers with diffraction limited beam quality are desired for many applications in defense and manufacturing. A lot of applications require laser beams at the 100 kW power level along with divergence close to the diffraction limit. The figure of merit for a beam used in such applications should be radiance which determines the laser power delivered to a remote target. One of the primary limiting factors is thermal distortion of a laser beam caused by excessive heat generated in the laser media. Combination of multiple laser beams is usually considered as a method to mitigate these limitations. Spectral beam combining (SBC) by volume Bragg gratings (VBGs) is a very promising method for the future of high radiance lasers that needs to achieve 100 kW-level power. This work is dedicated to development of methods to increase spectral density of combined beams keeping their divergence at an acceptably low level. A new figure of merit for a beam combining system is proposed, the Beam Combining Factor (BCF), which makes it possible to distinguish the quality of the individual beams from the quality of beam combining. Also presented is a method of including the effect of beam divergence and spectral bandwidth on the performance of VBGs, as well as a method to optimize VBG parameters in terms of thickness and refractive index modulation for an arbitrary number of beams. A novel thermal tuning technique and apparatus is presented with which the SBC system can be tuned for peak efficiency from low to high power without the need for mechanical re-alignment. Finally, a thermally tuned SBC system with five beams, with a spectral separation between beams of 0.25 nm at a total power of 685 W is presented. The results show the highest power spectral density and highest spectral radiance of any SBC system to date. Recent demonstrations in SBC by multiplexed VBGs and the use of super Gaussian beams for beam quality improvement are also discussed.
ID: 030646274; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 116-122).
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics

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Andrusyak, Oleksiy G. "Dense spectral beam combining with volume Bragg gratings in photo-thermo-refractive glass." Thesis, Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002662.

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Wang, Qing. "Single-Frequency and Mode-Locked Glass Waveguide Lasers and Fiber-Optic Waveguide Resonators for Optical Communications." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195101.

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Single-frequency and mode-locked silver film ion-exchanged glass waveguide lasers as well as all-optical clock recovery based on birefringent fiber resonators have been experimentally and theoretically studied. The theory, modeling and fabrication process of silver film ion-exchange techniques, have been discussed and presented.The UV-written gratings on both IOG-1 active and passive glass have been studied. For the first time, with a high quality narrowband grating UV-printed on the passive section of a hybrid glass, a DBR waveguide single-frequency laser is demonstrated with the linewidth less than 1 MHz and the output power of 9 mW.Novel saturable absorbers based on a fiber taper embedded in carbon nanotubes (CNTs)/polymer composite were demonstrated. The saturable absorbers were utilized to build mode-locked fiber lasers, which were studied experimentally. A mode-locked ring laser utilizing an Er-Yb-codoped glass waveguide as the gain medium was also demonstrated. In addition, short cavity mode-locked waveguide lasers with CNTs film on the top were theoretically investigated, which shows a short cavity mode-locked waveguide laser is very promising.A new concept to perform multi-channel multi-rate all-optical clock recovery based on birefringent fiber-optic waveguide resonators was discussed. The concept has been advanced to polarization-insensitive operation. The experimental results, obtained as a proof-of-concept, agree well with numerical simulations.

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Joshi, Sameehan Shrikant. "Non-Isothermal Laser Treatment of Fe-Si-B Metallic Glass." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062821/.

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Metallic glasses possess attractive properties, such as high strength, good corrosion resistance, and superior soft magnetic performance. They also serve as precursors for synthesizing nanocrystalline materials. In addition, a new class of composites having crystalline phases embedded in amorphous matrix is evolving based on selective crystallization of metallic glasses. Therefore, crystallization of metallic glasses and its effects on properties has been a subject of interest. Previous investigations from our research group related to laser assisted crystallization of Fe-Si-B metallic glass (an excellent soft magnetic material by itself) showed a further improvement in soft magnetic performance. However, a fundamental understanding of crystallization and mechanical performance of laser treated metallic glass was essential from application point of view. In light of this, the current work employed an integrated experimental and computational approach to understand crystallization and its effects on tensile behavior of laser treated Fe-Si-B metallic glass. The time temperature cycles during laser treatments were predicted using a finite element thermal model. Structural changes in laser treated Fe-Si-B metallic glass including crystallization and phase evolution were investigated with the aid of X-ray diffraction, differential scanning calorimetry, resistivity measurements, and transmission electron microscopy. The mechanical behavior was evaluated by uniaxial tensile tests with an InstronTM universal testing machine. Fracture surfaces of the metallic glass were observed using scanning electron microscopy and site specific transmission electron microscopy. Fe-Si-B metallic glass samples treated with lower laser fluence (<0.49 J/mm2) underwent structural relaxation while higher laser flounces led to partial crystallization. The crystallization temperature experienced an upward shift due to rapid heating rates of the order of 104 K/s during laser treatments. The heating cycle was followed by termination of laser upon treatment attainment of peak temperature and rapid cooling of the similar order. Such dynamic effects resulted in premature arrest of the crystallite growth leading to formation of fine crystallites/grain (~32 nm) of α-(Fe,Si) as the major component and Fe2B as the minor component. The structural relaxation, crystallization fractions of 5.6–8.6 Vol% with α-(Fe,Si) as the main component, and crystallite/grain size of the order of 12 nm obtained in laser fluence range of 0.39-0.49 J/mm2 had minimal/no influence on tensile behavior of the laser treated Fe-Si-B metallic glass foils. An increase in laser fluence led to progressive increase in crystallization fractions with considerable amounts of Fe2B (2-6 Vol%) and increase in grain size to ~30 nm. Such a microstructural evolution severely reduced the strength of Fe-Si-B metallic glass. Moreover, there was a transition in fracture surface morphology of laser treated Fe-Si-B metallic glass from vein pattern to chevron pattern. Tensile loading lacked any marked influence on the crystallization behavior of as-cast and structurally relaxed laser-treated metallic glass foils. However, a significant crystallite/grain growth/coarsening of the order of two and half times was observed in the fractured region compared to the region around it for the laser-treated partially crystallized metallic glass foils. The simultaneous effects of stress generation and temperature rise during tensile loading were considered to play a key role in crystallite/grain growth/coarsening.

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Kneis, Christian. "Investigation of mid-infrared supercontinuum generation in soft-glass fibers from a Q-switched mode-locked 2 mm fiber laser." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0135/document.

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Cette thèse est dédiée à l’étude de la génération de supercontinuum (SCG) deforte puissance moyenne dans le domaine spectral entre 2 mm et 5,5 mm. Un laser à fibredopée thulium (Tm3+) opérant dans un régime simultanément déclenché et à verrouillage demodes (QML) a été développé. En régime continu ce laser a délivré 70 W et en régime QML,26Wmoyens ont été obtenus pour des taux de répétition en QS de 180 kHz ou plus. L’énergiela plus élevée contenue dans une enveloppe QS a été évaluée à 166 mJ avec 66 mJ contenuedans la sous-impulsion à verrouillage de mode la plus énergétique. L’émission du laser àfibre correspondait toujours à un facteur de qualité M2 excellent, entre 1,1 et 1,2. La SCGcouvrant la plage spectrale de 2 mm à 5,5 mm a été réalisée en implémentant différentes fibresen cascade. Des supercontinua jusqu’à environ 4 mm ont été générés dans des fibres en fluorurepuis pour la plage spectrale complémentaire entre 4 mm et 5,5 mm, des fibres en chalcogénureont été utilisées.La puissance moyenne maximale de 7,8 W a été démontrée pour un supercontinuum dans unefibre en ZBLAN. Le spectre s’étend jusqu’à 4,2 mm. Au total, 69%/43%/30%/16,5% de lapuissance totale ont été mesurés au-delà de 2,15 mm/2,65 mm/3,1 mm/3,5 mm respectivement.La fibre en InF3 a permis d’atteindre une puissance moyenne de 0,8 W et le supercontinuums’étend jusqu’à 2,95 mm.Pour les essais d’élargissement spectral complémentaire, trois fibres en chalcogénure ont étéutilisées. L’élargissement spectral a été démontré pour toutes les fibres en chalcogénure.Jusqu’à 20 mW de puissance ont été obtenus avec une fibre As2Se3. Le spectre a été étendujusqu’à 4,9 mm
This thesis reports about the investigation of high power supercontinuum (SC)generation between 2 mm and 5.5 mm. A Q-switched mode-locked (QML) thulium (Tm3+)-doped fiber laser has been developped to pump different nonlinear fibers. The fiber laserprovided in continuous wave regime an output power of 70 W. In QML operation, 26 W havebeen obtained with Q-switched repetition rates of 180 kHz or higher. The highest energy of theQS envelopes has been 166 mJ with 66 mJ contained in the most-energetic ML pulses, whichhave been surrounded by Gaussian-like pedestals with temporal widths around 2.5 ns. On topof these pedestals, very short temporal peaks with pulse durations around 15 ps appeared. Thehighest achieved peak power of a pedestal has been 25 kW. The beam parameter product M2of the fiber laser has been measured in different operational regimes and resulted always in anexcellent value around 1.2.The highest SC output power level from a ZBLAN fiber has been 7.8 W. In total, 69%/43%/30%/16.5% of the transmitted SC output radiation could be converted beyond the wavelengthof 2.15 mm/2.65 mm/3.1 mm/3.5 mm, respectively, with the broadest output spectrum from theZBLAN fiber exceeding 4.2 mm. The InF3 fiber provided a total output power of 0.8 W withan output spectrum up to 2.95 mm.Successful broadening of the wavelength-limited SC output from the ZBLAN fibers has beenachieved with all three investigated chalcogenide fibers with as much as 20 mW of outputpower by using an arsenic selenide fiber. The output spectrum exceeded 4.9 mm

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Suo, Rui. "Advanced fibre gratings fabricated in standard and infrared glass fibres by ultraviolet and near-infrared- femtosecond lasers." Thesis, Aston University, 2009. http://publications.aston.ac.uk/11939/.

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In this thesis, I describe studies on fabrication, spectral characteristics and applications of tilted fibre gratings (TFGs) with small, large and 45° tilted structures and novel developments in fabrication of fibre Bragg gratings (FBGs) and long period gratings (LPGs) in normal silica and mid-infrared (mid-IR) glass fibres using near-IR femtosecond laser. One of the major contributions presented in this thesis is the systematic investigation of structures, inscription methods and spectral, polarisation dependent loss (PDL) and thermal characteristics of TFGs with small (<45°), large (>45°) and 45° tilted structures. I have experimentally characterised TFGs, obtaining relationships between the radiation angle, central wavelength of the radiation profile, Bragg resonance and the tilt angle, which are consistent with theoretical simulation based on the mode-coupling theory. Furthermore, thermal responses have been measured for these three types of TFGs, showing the transmission spectra of large and 45° TFGs are insensitive to the temperature change, unlike the normal and small angle tilted FBGs. Based on the distinctive optical properties, TFGs have been developed into interrogation system and sensors, which form the other significant contributions of the work presented in this thesis. The 10°-TFG based 800nm WDM interrogation system can function not just as an in-fibre spectrum analyser but also possess refractive index sensing capability. By utilising the unique polarisation properties, the 81 °-TFG based sensors are capable of sensing the transverse loading and twisting with sensitivities of 2.04pW/(kg/m) and 145.90pW/rad, repectively. The final but the most important contribution from the research work presented in this thesis is the development of novel grating inscription techniques using near-IR femtosecond laser. A number of LPGs and FBGs were successfully fabricated in normal silica and mid-IR glass fibres using point-by-point and phase-mask techniques. LPGs and 1st and 2nd order FBGs have been fabricated in these mid-IR glass fibres showing resonances covering the wavelength range from 1200 to 1700nm with the strengths up to 13dB. In addition, the thermal and strain sensitivities of these gratings have been systematically investigated. All the results from these initial but systematic works will provide useful function characteristics information for future fibre grating based devices and applications in mid-IR range.

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Anderson, Troy P. "Fabrication of integrated optofluidic circuits in chalcogenide glass using femtosecond laser direct writing." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4579.

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Femtosecond laser direct writing (FLDW) is a versatile process that uses focused femtosecond pulses to modify the physical structure of a material, which can result in a shift of optical properties such as the linear and nonlinear refractive index. If the photon energy of the femtosecond pulses lies below the material bandgap, nonlinear absorption rather than linear absorption becomes the dominant mechanism of energy transfer to the material. In this manner, a focused femtosecond pulse train can be used to fabricate functional features such as optical waveguides, diffractive optical elements, or micro-fluidic elements within the volume of a transparent medium. In this dissertation, the utility of femtosecond laser processing as a fabrication technique of optical and micro-fluidic elements in chalcogenide glasses is explored. The photo-induced modifications of optical and chemical parameters of new germanium-based Chalcogenide glasses in both bulk and thin-film form are characterized for the first time and the impact of material composition and laser fabrication parameters are discussed. The glasses are found to display an increase in volume, a decrease of the linear optical refractive index, and an increase of the nonlinear refractive index when exposed to femtosecond laser pulses. A model based on avalanche ionization and multi-photon ionization is used to describe the highly nonlinear absorption of laser light in the material and correlate the photo-induced modifications to the electron density generated during irradiation. The magnitude of the induced photo-modification is shown to be dependent on laser parameters such as laser dose and repetition rate. The fabrication of microfluidic elements through both direct ablation and the preferential etching of photo-modified regions is also explored. Finally, the integration of both optical elements and fluidic elements fabricated by FLDW into a single substrate is discussed.
ID: 028916651; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 181-194).
Ph.D.
Doctorate
Optics

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Lantigua, Christopher. "Metrology of Volume Chirped Bragg Gratings Recorded in Photo-Thermo-Refractive Glass for Ultrashort Pulse Stretching and Compressing." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5803.

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Chirped Bragg gratings (CBGs) recorded in photo-thermo-refractive (PTR) glass provide a very efficient and robust way to stretch and compress ultra-short laser pulses. These gratings offer the ability to stretch pulses from hundreds of femtoseconds, to the order of 1 ns and then re-compress them. However, in order to achieve pulse stretching of this magnitude, 100 mm thick CBGs are needed. Using these CBGs to both stretch, and re-compress the pulse thus requires propagation through 200 mm of optical glass. This therefore demands perfect control of the glass homogeneity, as well as the holographic recording process of the CBG. In this thesis, we present a study of the CBG parameters that lead to distortions in the quality of diffracted beams. We first present the challenges associated with measuring the quality of these beams and we show that such measurements are not easily achieved using commercial systems that rely on the ISO standard M2 method. Thus, we introduce a new metric of beam quality, which we have coined S2, that is a combination of both the M2 and power in the bucket metrics. Subsequently, we investigate the influence of the CBG parameters on the quality of diffracted beams. In particular, we examine the impact of small optical heterogeneities known as striae, as well as the impact of the optically and thermally induced distortions in the grating. We then use this data to improve the fabrication and characterization of 100 mm long CBGs. Finally, we characterize the performance of CBGs recorded in PTR for stretching and compression of femtosecond pulses using a custom autocorrelation system. We present data on high quality 100 mm long CBGs and an analysis on the correlation between beam quality and the final pulse duration after stretching and re-compressing the pulse.
M.S.
Masters
Optics and Photonics
Optics and Photonics
Optics

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Mansour, Nastaran. "Nonlinear Absorption Initiated Laser-Induced Damage in [Gamma]-Irradiated Fused Silica, Fluorozirconate Glass and Cubic Zirconia." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc331327/.

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The contributions of nonlinear absorption processes to laser-induced damage of three selected groups of transparent dielectrics were investigated. The studied materials were irradiated and non-irradiated fused silica, doped and undoped fluorozirconate glass and cubic zirconia stabilized with yttria. The laser-induced damage thresholds, prebreakdown transmission, and nonlinear absorption processes were studied for several specimens of each group. Experimental measurements were performed at wavelengths of 1064 nm and 532 nm using nanosecond and picosecond Nd:YAG laser pulses. In the irradiated fused silica and fluorozirconate glasses, we found that there is a correlation between the damage thresholds at wavelength λ and the linear absorption of the studied specimens at λ/2. In other words, the laser-induced breakdown is related to the probability of all possible two-photon transitions. The results are found to be in excellent agreement with a proposed two-photon-initiated electron avalanche breakdown model. In this model, the initial "seed" electrons for the formation of an avalanche are produced by two-photon excitations of E' centers and metallic impurity levels which are located within the bandgaps of irradiated Si02 and fluorozirconate glasses, respectively. Once the initial electrons are liberated in the conduction band, a highly absorbing plasma is formed by avalanche impact ionization. The resultant heating causes optical damage. In cubic zirconia, we present direct experimental evidence that significant energy is deposited in the samples at wavelength 532 nm prior to electron avalanche formation. The mechanism is found to be due to formation of color centers (F+ or F° centers) by the two-photon absorption process. The presence of these centers was directly shown by transmission measurements. The two-photon absorption (2PA) process was independently investigated and 2PA coefficients obtained. The accumulated effects of the induced centers on the nonlinear absorption measurements were also considered and the 2PA coefficients were measured using short pulses where this effect is negligible. At room temperature, the color centers slowly diffuse out of the irradiated region. The density of these centers was monitored as a function of time. The initial distribution of the centers was assumed to have a Gaussian profile. For this model the diffusion equation was solved exactly and the diffusion constant obtained.

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BOMFIM, JUNIOR FRANCISCO A. "Producao e caracterizacao de vidros de oxidos de metais pesados dopados com terras-raras e nanoparticulas metalicas." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9433.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Ouslimani, Hana. "Intégration de lasers impulsionnels monofréquences sur verre phosphate dopé ytterbium." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT100/document.

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De nombreux capteurs optiques, tels que les LIDARS, nécessitent des sources laser à la fois puissantes et spectralement fines. Dans ce contexte, l'objectif de ce projet est la réalisation de sources laser impulsionnelles intégrées, dont les caractéristiques spectrale et temporelle atteignent la limite théorique prédite par la théorie de Fourier. Pour ce faire, nous proposons une structure laser de type DFB avec un fonctionnement déclenché. La technologie de l'échange d'ions est retenue pour réaliser des guides d'onde amplificateurs dans un verre phosphate dopé ytterbium. La cavité DFB est ensuite constituée par gravure d'un réseau de Bragg à la surface des guides amplificateurs. Le comportement impulsionnel est obtenu par dépôt, sur la structure précédente, d'une couche mince d'acétate de cellulose dopée avec l'absorbant saturable BDN. Cette structure nous a permis d'obtenir des lasers impulsionnels monomodes longitudinaux dont les caractéristiques spectrales atteignent la limite de Fourier. Une étude en concentration d'absorbant saturable du superstrat montrent une variation de la durée des impulsions de 2,5 ns à 100 ns avec des puissances crêtes respectives de 30 W et 14 W. Nous parvenons donc à des spectres de largeur à mi-hauteur de valeur 9 MHz. Ces résultats ouvrent la voie à la réalisation de sources laser compactes pour les lidars embarqués
Various optical sensors, such as LIDARs, need laser sources both powerful and narrow-linewidth. In this context, the aim of this project is the realization of integrated pulsed laser sources with a Fourier Transform Limited (FTL) spectrum. To do so, we propose a passively Q-switched DFB laser structure. Ion-exchange technology is used to realize amplifier waveguides on Ytterbium-doped phosphate glass. The DFB cavity is made by dry etching of a Bragg grating on the waveguides surface. The Q-Switched behavior is obtained by depositing a BDN-doped cellulose acetate coating layer, acting as a saturable absorber. This structure allowed us obtaining FTL single-frequency pulsed lasers. When studying the impact of BDN concentration, we observe pulses ranging from 2,5 ns with 40 W peak power, to 100 ns with 14 W peak power. Thus, our device FWHM linewidth goes down to 9 MHz. These results pave the way for the realisation of compact laser sources for embedded lidar systems

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Jebahi, Mohamed. "Discrete-continuum coupling method for simulation of laser-inducced damage in silica glass." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14911/document.

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Une méthode de couplage continu-discret a été développée pour simuler les mécanismes complexes d'endommagement de la silice soumise à un choc laser de haute puissance. Dans un premier temps, une classification des méthodes numériques existantes a été faite pour choisir celles les mieux adaptées à la simulation du comportement sous choc de la silice. Comme résultat de cette classification, deux méthodes ont été retenues: la méthode des éléments discrets (DEM) et la méthode des éléments naturels contraints (CNEM). Ces méthodes sont alors couplées en se basant sur la technique dite "Arlequin". Puis, un modèle numérique permettant de tenir compte des différents phénomènes qui caractérise le comportement de la silice sous haute pression a été développé. Pour bien caractériser les mécanismes de fissuration de la silice à l’échelle microscopique, un nouveau modèle de rupture a été développé dans ce travail. Finalement, ces deux modèles, modèle de comportement et modèle de rupture, ont été intégrés dans la méthode du couplage pour simuler d'un point de vue mécanique le choc laser sur un échantillon en silice
A discrete-continuum coupling approach has been developed to simulate the laser-induced damage in silica glass. First, a classification of the different numerical methods has been performed to select the ones that best meet the objectives of this work. Acting upon this classification, the Discrete Element Method (DEM) and the Constrained Natural Element Method (CNEM) have been retained. Subsequently, a coupling approach between these methods has been proposed. This approach is based on the Arlequin technique. In the second part, a numerical model of the silica glass mechanical behavior has been developed to better characterize the silica glass response under highly dynamic loadings and particularly loading generated by a laser beam. To correctly characterize the silica glass cracking mechanisms, a new fracture model has been proposed in this work. Finally, all these developments have been used to simulate the laser-induced damage in silica glass

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ROSSI, RIVELY R. "Avaliação da microinfiltração marginal apos preparos cavitários realizados com laser ER,Cr:YSGG e alta rotação em dentes deciduos, restaurados com diferentes cimentos de ionomero de vidro." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11393.

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Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia)
IPEN/D-MPLO
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP; Faculdade de Odontologia, Universidade de Sao Paulo

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35

STREFEZZA, CLAUDIA. "Análise da resistência de união adesiva de retentores intrarradiculares metálicos e estéticos cimentados em condutor irradiado com laser de diodo de alta potência (830mm)." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10562.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Souza-e-Silva, Cintia Maria de. "Efeitos do laser de CO2 na desmineralização do esmalte ao redor de braquetes ortodonticos." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288092.

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Orientador: Marines Nobre dos Santos Uchoa
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: A aplicação do laser de dióxido de carbono (CO2) à estrutura do esmalte modifica a composição química e/ou morfológica dessa superfície e inibe o desenvolvimento e a progressão de lesões cariosas. Porém, não foram realizadas pesquisas que tenham verificado se a irradiação do esmalte dental ao redor de braquetes ortodônticos com esse laser é efetiva em reduzir a desmineralização nessa região numa situação de alto desafio cariogênico. Assim, esta dissertação objetivou verificar, in vitro, se a irradiação do esmalte dental com laser de CO2 (?=10.6 µm e 10.0 J/cm2), associada ou não a liberação de fluoreto pelo material de colagem, seria capaz de reduzir a perda mineral do esmalte, ao redor de braquetes ortodônticos, quando submetido a uma situação de alto desafio cariogênico. Nesse estudo, 24 blocos de esmalte bovino foram divididos em 4 grupos, em triplicata: 1 ¿ resina composta não liberadora de fluoreto Transbond (T); 2 ¿ cimento de ionômero de vidro modificado por resina Fuji (F); 3 ¿ laser de CO2 + resina composta não liberadora de fluoreto (TL); 4 ¿ laser de CO2 + cimento de ionômero de vidro modificado por resina (FL). Um grupo contendo blocos de esmalte foi incluído apenas para análise de microdureza. Após a colagem dos braquetes, os espécimes foram suspensos em água destilada deionizada esterilizada e esterilizados com radiação gama. A seguir, foram transferidos para o meio de cultura esterilizado de caldo de cérebro-coração (BHI) contendo sacarose a 5% e os 4 grupos experimentais foram inoculados com uma cultura overnight de Streptococcus mutans. Diariamente, o meio BHI foi trocado e analisado quanto à contaminação microbiológica. Após 6 dias de incubação (37ºC - 10% CO2), o biofilme foi coletado e submetido as análises microbiológica (UFC/mg) e bioquímica. Além disso, microdureza do esmalte seccionado longitudinalmente foi determinada. Os dados foram analisados pelos testes ANOVA e Tukey, com alfa a 5%. As concentrações de polissacarídeo insolúvel em água (µg/mg) no biofilme foram: T ¿ 213,206(±421,746)a, F ¿ 111,208(±43,501)a, TL ¿ 124,626(±37,488)a e FL ¿ 138,83(±118,893)a. As concentrações de cálcio (µg/mg) foram: T ¿ 340,5(±27,01)a, F ¿ 329,5(±143,97)a, TL ¿ 412,3(±228,80)a e FL ¿ 411,8(±252,59)a. As concentrações de fluoreto (µg/mg) no biofilme foram: T ¿ 0,001(±0,005) a, F ¿ 0,010(±0,021) a, TL ¿ 0,0009(±0,002)a e FL ¿ 0,002(±0,007)a. As concentrações de fósforo (µg/mg) foram: T ¿ 0,162(±0,134)a, F ¿ 0,149(±0,066)a, TL ¿ 0,170(±0,104)a a e FL ¿ 0,148(±0,029)a. Os resultados (expressos 107 UFC/mg) obtidos da análise microbiológica foram: T ¿ 2,54(±2,58)a, F ¿ ,90(±3,08)a, TL ¿ 2,59(±3,13)a e FL ¿ 2,30(±4,04)a. A média numérica da microdureza knoop (kg/mm2) variou de 195,5(±87,3)c, 209,8(±75,0)bc, 218,2(±113,6)ab e 229,1(±82,7)a para os grupos T, F, TL e FL, respectivamente. Em conclusão, esse estudo demonstrou que o uso do laser de CO2 (?=10.6 µm e 10.0 J/cm2) sozinho ou combinado com o material de colagem liberador de fluoreto foi capaz de reduzir a perda mineral do esmalte ao redor de braquetes ortodônticos, quando submetidos a uma situação de alto desafio cariogênico com biofilme de Streptococcus mutans.
Abstract: The application of carbon dioxide laser (CO2) on dental enamel structure modifies the chemical and/or morphologic composition of this surface and inhibits the development and progression of caries lesion. However, no research verified the if the irradiation of dental enamel around orthodontic brackets was able to reduce the enamel mineral loss in this region in a high cariogenic challenge. Thus, this dissertation aimed to verify in vitro, if the irradiation of the dental enamel with a laser of CO2 (? =10.6 µm and 10.0 J/cm2), associated or not with fluoride released from a bonding material, will be able to reduce the enamel mineral loss around orthodontic brackets, when submitted to a high cariogenic challenge situation. In this study, twenty four enamel slabs were divided into 4 groups in triplicate: 1. nonfluoride-releasing composite resin Transbond (T); 2. resinmodified glass ionomer cement Fuji (F); 3. CO2 laser + nonfluoride-releasing composite resin (TL); 4. CO2 laser + resin-modified glass ionomer cement (FL). One group with 6 specimens of sound enamel were used to determine the sound enamel microhardness. After brackets bonding, the specimens were immersed in sterile deionized distilled water and sterilized with gamma radiation. Following, the specimens were transferred to a sterile brain-heart infusion broth (BHI) with a 5% sucrose solution and the 4 experimental groups were inoculated with an overnight culture of Streptococcus mutans. The BHI medium was daily changed and analyzed to check for microbiological contamination. After 6 days of incubation (37ºC - 10% CO2), the biofilm was collected and submitted to microbiological (CFU/mg) and biochemical analyses. Additionally, microhardness assay of the enamel longitudinally sectioned was determine. The data were statistically analyzed by the ANOVA and Tukey¿ tests, with an alpha of 0.05. The concentrations of water-insoluvel polysaccharide (µg/mg) in biofilm were: T ¿ 213.206(±421.746)a, F ¿ 111.208(±43.501)a, TL ¿ 124.626(±37.488)a e FL ¿ 138.83(±118.893)a. The concentrations of calcium (µg/mg) were: T ¿ 340.5(±27.01)a, F ¿ 329.5(±143.97) a, TL ¿ 412.3(±228.80)a e FL ¿ 411.8(±252.59) a. The concentrations of fluoride (µg/mg) in biofilm were: T ¿ 0.001(±0.005) a, F ¿ 0.010(±0.021)a, TL ¿ 0.0009(±0.002)a e FL ¿ 0.002(±0.007)a. The concentrations of phosphorus (µg/mg) were: T ¿ 0.162(±0.134)a, F ¿ 0.149(±0.066)a, TL ¿ 0.170(±0.104)a e FL ¿ 0.148(±0.029)a. The results (expressed 107 CFU/mg) obtained of microbiological analysis were: T ¿ 2.54(±2.58)a, F ¿ 2.90(±3.08)a, TL ¿ 2.59(±3.13)a e FL ¿ 2.30(±4.04)a. The mean knoop microhardness number (kg/mm2) varied from 195.5(±87.3)c,209.8(±75.0)bc, 218.2(±113.6)ab and 229.1(±82.7)a for T, F, TL and FL respectively. In conclusion, the present study demonstrated that the use CO2 laser (?=10.6 µm and 10.0 J/cm2) alone or combined with the release of fluoride by bonding material was capable of reducing the enamel mineral loss around the orthodontic brackets, when submitted to a high microbiological cariogenic challenge with a Streptococcus mutans biofilm.
Mestrado
Odontopediatria
Mestre em Odontologia

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37

Choi, Ji Yeon. "Ecriture par Laser de fonctionnalités optiques : éléments diffractifs et ONL." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00583861.

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A la suite de la première démonstration de l'écriture de guide d'onde au sein de verres en 1996 par laser femtoseconde, l'écriture direct par Laser Femtoseconde (Femtoseconde Direct Laser Writing - FLDW) est apparu comme une technique souple pour la fabrication de structure photonique en trois dimensions au sein de matériaux pour l'optique. La thèse a porté sur l'inscription par laser femtoseconde de fonctionnalités optiques au sein de verres. Des éléments diffractifs par modification de l'indice de réfraction et des structures présentant des propriétés de luminescence ou d'optique non linéaire d'ordre deux ont pu être obtenus au sein de matériaux vitreux et étudiés.

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Pomarede, Damien. "Fibres optiques vitrocéramiques pour application laser." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0019/document.

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Cette thèse porte sur le développement de fibres optiques de type cœur/gaine, dont le cœur est composé de vitrocéramiques transparentes. Le système étudié est composé d’une matrice de silice stabilisant la phase ZnGa2O4 sous la forme de nano cristaux, pouvant être dopés par des ions de métaux de transition tels que le chrome (III) et le nickel (II). Les verres précurseurs de vitrocéramiques ont été synthétisés par fusion trempe, étirés sous forme de fibres optiques par la méthode poudre puis recuits thermiquement afin d’obtenir des fibres optiques à cœur vitrocéramiques optiquement actives. L’optimisation conjointe de la composition des verres précurseurs, des paramètres de fibrage, de la composition finale des fibres et du protocole de recuit thermique de cristallisation, ont permis de maximiser leurs propriétés de luminescence autour de 700 nm et 1350 nm pour les fibres dopées par du chrome (III) et du nickel (II) respectivement. Ces types de fibres peuvent trouver des applications dans les domaines de la thermométrie optique, des sources optiques, des amplificateurs et des lasers fibrés. En particulier, nous avons démontré que le spectre d’émission autour de 1350 nm des fibres dopées par du nickel (II) présente une largeur à mi-hauteur supérieure à 270 nm, meilleure que celle des sources commerciales centrées autour de 1300 nm. Le niveau de puissance émise, de l’ordre d’une trentaine de microwatts, est quasiment compatible avec les applications de source optique pour l’OCT. Des développements ultérieurs visant à réduire le niveau de pertes dans ces fibres et de maximiser l’efficacité du dopant permettrons d’amener cette technologie à un niveau de performance compatible avec ces applications. Ces résultats encourageants ont motivés le dépôt d’une demande de protection des fibres et de leur procédé d’élaboration par un brevet
This thesis focuses on the development of core/clad type optical fibers where the core is composed of transparent glass ceramics. The system considered was composed of a silica matrix where ZnGa2O4 nanocrystals can be stabilized. Those crystals can interestingly be doped with transition metal ions such as chromium (III) or nickel (II) ions. The precursor glass were synthetized by melt quenching method, drawn into fibers through the powder in tube process, and subsequently annealed to produce optically active glass ceramic optical fibers. The starting glass composition together with the drawing parameters, the fiber core composition and the annealing protocol were optimized in order to maximize the luminescence properties around 700 nm and 1350 nm in chromium (III) and nickel (II) doped fibers respectively. Such type of fibers are interesting for the domains of optical thermometry, fibered sources, amplifiers and lasers. In particular, we demonstrated that the emission spectrum around 1350 nm of nickel (II) doped glass ceramic fibers exhibited a full width at half maximum above 270 nm, wider than that of 1300 nm centered commercial sources. The overall power outcome is about thirty micro watts, which is almost suitable for OCT applications. Further developments aiming at reducing the optical losses in the fibers and in maximizing the dopant efficiency will allow to reach the applications requirements. Those promising results led to a patent application on the fibers composition and their fabrication process

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Chen, Jianyong. "Ultrafast laser microwelding of glass-to-glass and glass-to-opaque materials." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3335.

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Techniques for joining materials, especially glass to dissimilar materials, while maintaining their surface and optical properties are essential for a wide range of industrial applications. Current techniques rely on adhesives or interlayers which can exhibit issues with creep, out-gassing or aging. Ultrafast laser welding based on nonlinear absorption in transparent material offers an attractive solution to this problem. Bringing two material surfaces into close (optical) contact and focusing the ultrafast laser onto the interface allows for localised melting and rapid resolidification, forming strong bond and welding the two surfaces together. The highly localised nature of this absorption means that welds can be created whilst avoiding significant heating of the surrounding material―important for joining materials with significantly different thermal expansion coefficients. Using a picosecond laser system (Trumpf TruMicro), a range of welds between similar material (borosilicate glass to borosilicate glass, fused silica to fused silica, borosilicate glass to fused silica) and highly dissimilar materials (sapphire to stainless steel, fused silica/borosilicate glass to silicon/aluminium/copper/stainless steel) have been demonstrated. Theoretical simulations were carried out to investigate the aberrations that occur to a laser beam focused inside material and to describe the behaviour of the generated plasma. With the guidance of theoretical work and developed experiment setup, a large range of parameters related to welding were investigated both in bulk material and welding for different materials and surface conditions. Shear strength tests on welds shows a maximum value could be obtained between parameters resulting in barely welded seams, for low power, and obvious cracking, for higher power. Optimised welding for borosilicate to borosilicate glass creates stronger bonds (108.8 N/mm2) than traditional joining methods (adhesive, typically 15~25 N/mm2). Parameter maps were made for different surface separation and surface conditions to determine a successful weld. In order to weld highly dissimilar materials, different welding patterns were designed to relax residual stress and eliminate cracks. Welding with galvo-scanner was also introduced as an alternative method for industrial applications which provides a high scan speed and flexible patterns. To increase welding strength and expand the parameter tolerance for a successful welding, focus vibration methods were proposed to reduce the residual stress. Finally, welding of example industrial parts was demonstrated for different application requirements.

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Holmberg, Patrik. "Laser processing of Silica based glass." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.

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The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.
Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.

QC 20150924

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Nisar, Salman. "Diode laser cutting of float glass." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508981.

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JAGOSICH, FABIO H. "Estudos dos processos de transferência de energia dos íons de Ersup(3+) e Hosup(3+) para os íons de Ndsup(3+), Tbsup(3+) e Eusup(3+) no cristal de LiYFsub(4) e no vidro ZBLAN para a otimização de meios laser ativos que operam na região de 3 microns." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11432.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/11446-0

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Stillman, Janet Allyn. "Three-dimensional microfabrication with laser-patterned photostructurable glass." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1779690371&sid=28&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Fateri, Miranda [Verfasser]. "Selective Laser Melting of Glass Powders / Miranda Fateri." München : Verlag Dr. Hut, 2018. http://d-nb.info/1155056159/34.

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45

Rivers, Paul Edmund. "Pulsed laser deposition of chalcogenide glass materials for potential waveguide laser applications." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/15493/.

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There are many applications for small scale, solid state lasers in the near infrared, where conversely there are very few such devices. A lasing device in a rare earth doped gallium-lanthanum-sulphide thin film is attractive due to emission at wavelengths in the 2 to 5 µm region where many gasses and liquids have fundamental vibrations and overtones and so are detectable. This region also covers the 3 to 5 µm atmospheric 'windows'. Some examples of such detection is presented in this thesis. Using Pulsed Laser Deposition, a relatively new deposition technique, we are able to grow thin films of the chalcogenide glass; gallium-lanthanum-sulphide, gallium-sodium-sulphide and variations of oxysulphides, on a variety of substrates. EXAFS measurements have shown that some of the elements in the glass structure change their bonding arrangement when grown at different energy density producing 'wrong bonds'. This points to the origin of the increased absorption and shift of the optical bandgap which is seen in the materials. It is this tail absorption which ultimately prevented the production of an actual solid state, rare earth laser device. These amorphous semiconductors have a transmission range from the visible through to the mid infrared part of the spectrum. Chalcogenides can be photomodified. i.e. they have an ability to change refractive index when illuminated with photons whose energies lie in the optical bandgap of the material. This process can be reversible or irreversible depending on post deposition treatment and so gives them potential applications such as optical memory, holographic recording media, lithographically written waveguide structures and potentially laser mediums. For such uses a detailed knowledge of the chalcogenide materials optical parameters is needed. A novel technique for the optical characterisation of the thin films has been developed which has is able to measure differences in refractive index to an accuracy of 8.5 x 105. We are able to map refractive index changes across an entire surface and more uniquely whilst they are occurring during, and after, photomodification or heating.

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Ratsibi, Humbelani Edzani. "Laser drilling of metals and glass using zero-order bessel beams." University of the Western Cape, 2013. http://hdl.handle.net/11394/5428.

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>Magister Scientiae - MSc
This dissertation consists of two main sections. The first section focuses on generating zero order Bessel beams using axicons. An axicon with an opening angle y = 5⁰ was illuminated with a Gaussian beam of width ω₀ = 1.67 mm from a cw fiber laser with central wavelength λ = 1064 nm to generate zero order Bessel beams with a central spot radius r₀ = 8.3 ± 0.3 μm and propagation distance ½zmax = 20.1 ± 0.5 mm. The central spot size of a Bessel beam changes slightly along the propagation distance. The central spot radius r₀ can be varied by changing the opening angle of the axicon, y, and the wavelength of the beam. The second section focuses on applications of the generated Bessel beams in laser microdrilling. A Ti:Sapphire pulsed femtosecond laser (λ = 775 nm, ω₀ = 2.5 mm, repetition rate kHz, pulse energy mJ, and pulse duration fs) was used to generate the Bessel beams for drilling stainless steel thin sheets of thickness 50 μm and 100 μm and microscopic glass slides 1 mm thick. The central spot radius was r₀ = 15.9 ± 0.3 μm and ½zmax = 65.0 ± 0.5 mm. The effect of the Bessel beam shape on the quality of the holes was analysed and the results were discussed. It was observed that Bessel beams drill holes of better quality on transparent microscopic glass slides than on stainless steel sheet. The holes drilled on stainless steel sheets deviated from being circular on both the top and bottom surface for both thicknesses. However the holes maintained the same shape on both sides of each sample, indicating that the walls are close to being parallel. The holes drilled on the glass slides were circular and their diameters could be measured. The measured diameter (15.4±0.3 μm) of the hole is smaller than the diameter of the central spot (28.2 ± 0.1 μm) of the Bessel beam. Increasing the pulse energy increased the diameter of the drilled hole to a value close to the measured diameter of the central spot.

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Siiman, Leo. "ULTRASHORT LASER PULSE INTERACTION WITH PHOTO-THERMO-REFRACTIVE GLASS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3946.

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Photo-thermo-refractive (PTR) glass is an ideal photosensitive material for recording phase volume holograms. It is a homogeneous multi-component silicate glass that demonstrates all the advantages of optical glass: thermal stability, high laser damage threshold, and a wide transparency range. Moreover the ability to record phase patterns (i.e. spatial refractive index variations) into PTR glass has resulted in the fabrication of volume holograms with diffraction efficiency greater than 99%. The conventional method of recording a hologram in PTR glass relies on exposure to continuous-wave ultraviolet laser radiation. In this dissertation the interaction between infrared ultrashort laser pulses and PTR glass is studied. It is shown that photosensitivity in PTR glass can be extended from the UV region to longer wavelengths (near-infrared) by exposure to ultrashort laser pulses. It is found that there exists a focusing geometry and laser pulse intensity interval for which photoionization and refractive index change in PTR glass after thermal development occur without laser-induced optical damage. Photoionization of PTR glass by IR ultrashort laser pulses is explained in terms of strong electric field ionization. This phenomenon is used to fabricate phase optical elements in PTR glass. The interaction between ultrashort laser pulses and volume holograms in PTR glass is studied in two laser intensity regimes. At intensities below ~10^12 W/cm^2 properties such as diffraction efficiency, angular divergence, selectivity, and pulse front tilt are shown to agree with the theory of linear diffraction for broad spectral width lasers. A volume grating pair arrangement is shown to correct the laser pulse distortions arising from pulse front tilt and angular divergence. At higher intensities of irradiation, nonlinear generation and diffraction of third harmonic is observed for three types of interactions: sum-frequency generation, front-surface THG generation, and THG due to phase-matching with a grating formed by modulation of the nonlinear refractive index of PTR glass.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD

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48

Xiao, Kun. "Indirect selective laser sintering of Apatite-Wollastonite glass-ceramic." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441221.

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49

Schmidt, Torsten. "Identifizierung und Untersuchung pharmazeutischer Gläser durch Laser-Ablation-ICP-MS." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2001. http://dx.doi.org/10.18452/14655.

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Die chemische Zusammensetzung pharmazeutisch verwendeter Gläser (Ampullen, Infusionsglas, Fertigspritzenbehältnisse) wurde mit Laser-Ablation-ICP-Massenspektrometrie (LA-ICP-MS) untersucht. Dazu kam ein Nd:YAG-Laser mit einer Frequenz von 10 Hz im q-switch mode mit der Grundwellenlänge sowie der 4. Harmonischen (1064 und 266 nm) zum Einsatz. Ziel war die Identifizierung verschiedener Arten pharmazeutisch eingesetzter Gläser. Folgende Isotope wurden zur Charakterisierung bestimmt: 7Li, 11B, 23Na, 24Mg, 27Al, 28Si, 29Si, 30Si, 39K, 42Ca, 47Ti, 57Fe, 90Zr, 121Sb, 137Ba. Die quantitativen Ergebnisse zeigten relative Standardabweichungen von 1.8 % bis 8.0 %. Die Normierung der Daten erfolgte unter Bezug auf 29Si. Mit Referenzmaterial verschiedener Zusammensetzung (Natron-Kalk-Glas, Borosilikatglas und Bleiglas) wurden externe Mehrpunktkalibrationen erstellt. Für alle gemessenen Isotope konnten lineare Kalibrierfunktionen festgestellt werden. Die Richtigkeit des Verfahrens wurde durch Aufschluß des Standardmaterials wie auch der untersuchten Proben mit Flußsäure/Salpetersäure und Messung der Aufschlußlösungen nach externer Kalibration durch Multielement-Standards gezeigt. Aufschluß- und Laserablation-Ergebnisse zeigten gute Übereinstimmung und wichen um bis zu 8 % voneinander ab. Zur Prüfung repräsentativer Ablation der Proben wurden die Isotopenverhältnisse bestimmt. Auch hier zeigte sich eine ausreichende Übereinstimmung mit den theoretischen Werten. Weiterhin wurden Präzision, Empfindlichkeit, Selektivität, Nachweisgrenze, Bestimmungsgrenze und Robustheit des Verfahrens bestimmt. Im Unterschied zu den Ergebnissen unter der Grundwellenlänge führte die Verwendung der Laserwellenlänge 266 nm zu keinen signifikanten Verbesserungen der Resultate. Die Aufnahme transienter Signale sollte zur Erkennung von Elementverteilungen in Glasoberflächen dienen. Am Beispiel eines Natron-Kalk-Glases wurden in einzelnen Schichten verschiedene Elementkonzentrationen festgestellt. Weiterhin konnten mit dieser Technik Glasampullen erkannt werden, deren Oberflächen durch ein Silikonisierungsverfahren vergütet waren. Zum Abschluß der Untersuchungen wurde versucht, auf Grundlage der unnormierten Intensitätsdaten der LA-Messungen Gläser zu klassifizieren. Hierzu wurde die lineare Diskriminanzanalyse eingesetzt, mit deren Hilfe nach Variablenreduktion (8 von 13 Isotopen) alle eingesetzten Glasarten korrekt identifiziert werden konnten. Durch das entwickelte und validierte LA-ICP-MS-Verfahren steht eine leistungsfähige Technik zur quantitativen Untersuchung der chemischen Zusammensetzung von Gläsern sowie zur Identifizierung der jeweiligen Glassorte zur Verfügung.
The chemical composition of pharmaceutical glasses (ampoules, infusion bottles, plunger) has been determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). A Nd:YAG laser with 10 Hz repetition rate in the q-switch mode at its fundamental wavelength and its 4th harmonic (1064 and 266 nm) was used to identify common types of pharmaceutical glasses. The following isotopes were used for measurements: 7Li, 11B, 23Na, 24Mg, 27Al, 28Si, 29Si, 30Si, 39K, 42Ca, 47Ti, 57Fe, 90Zr, 121Sb, 137Ba. Relative standard deviations between 1.8 % and 8.0 % of the quantitative results were obtained. 29Si was used as internal standard. Standard reference materials (soda-lime-, lead- and borosilicate glasses) were used for external calibration of laser sampling. Linear calibration functions for each isotope were found. The accuracy was determined by digestion of all samples and standard materials in a two-step-procedure by nitric/fluoric acid, measurement and external calibration by ICP-MS with multi-elemental standard solutions. Digestion and laser ablation results agreed within 8 % with the certified values. The proof of representative ablation was given by sufficient agreement of intensity ratios of most isotopes with the corresponding theoretical values. Further precision, sensititivity, selectivity, limit of detection, limit of quantitation and robustness were determined. In contrast to the fundamental wavelength the laserablation technique with 266 nm showed no significant improvement in the quality of the results. By measuring transient signals element concentrations of surface layers should be detected. Differing concentrations could be determined in soda-lime-glass samples. Also different surface-treated borosilicate-glass ampoules were examined by this method. Silicon-treated glass surfaces could be identified. Finally raw data of LA measurements were used for applying linear discriminant analysis. After reduction of the used variables (8 of 13 isotopes) all types of glasses could be distinguished only by their intensity data of LA measurements. The developed LA-ICP-MS method is a powerful technique to distinguish different types of pharmaceutical glasses and to examine their chemical composition.

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50

He, Baofeng. "Characterization and improvement of copper/glass adhesion." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10056.

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The development of glass substrates for use as an alternative to printed circuit boards (PCBs) attracts significant industrial attention, because of the potential for low cost but high performance interconnects and optical connection. Electroless plating is currently used to deposit conductive tracks on glass substrates and the quality of copper / glass adhesion is a key functional issue. Without adequate adhesive strength the copper plating will prematurely fail. Existing studies have covered the relationship between surface roughness and adhesion performance, but few of them have considered the detail of surface topography in any depth. This research is specifically considering the mechanical contribution of the glass surface texture to the copper / glass adhesive bond, and attempting to isolate new ISO 25178 areal surface texture parameters that can describe these surfaces. Excimer laser machining has been developed and used to create a range of micro pattern structured surfaces on CMG glass substrates. Excimer mask dimensions and laser operation parameters have been varied and optimized according to surface topography and adhesion performance of the samples. Non-contact surface measurement equipment (Zygo NewView 5000 coherence scanning interferometry) has been utilized to measure and parameterize (ISO 25178) the surface texture of the glass substrates before electroless copper metallization. Copper adhesion quality has been tested using quantitative scratch testing techniques, providing an identification of the critical load of failure for different plated substrates. This research is establishing the statistical quality of correlation between the critical load values and the associated areal parameters. In this thesis, the optimal laser processing parameter settings for CMG glass substrate machining and the topographic images of structured surfaces for achieving strong copper / glass plating adhesion are identified. The experimental relationships between critical load and areal surface parameters, as well as the discussions of a theoretical approach are presented. It is more significant to consider Sq, Sdq, Sdr, Sxp, Vv, Vmc and Vvc to describe glass substrate surface topography and the recommended data value ranges for each parameter have been identified to predict copper / plating adhesion performance.

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