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1
Aubourg, Adrien. "Sources laser à fibre cristalline YAG dopée erbium et pompée par diode". Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0008/document.
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Parmi les nombreuses applications des sources laser, certaines nécessitent une propagation du faisceau dans l'atmosphère sur plusieurs kilomètres : télémétrie, désignation, ou encore imagerie active. Pour éviter tout risque oculaire tout en proposant de plus grandes portées, ces applications doivent faire appel à des sources laser émettant une longueur d'onde dans la gamme à sécurité oculaire autour d'un minimum local d'absorption de l'atmosphère (1550-1650 nm). De telles sources existent déjà commercialement, mais ne répondent pas aux exigences militaires de compacité, de consommation électrique, de performance et de fonctionnement sur une large gamme de température (-40°C/+60°C).Mes travaux de thèse tentent d'apporter une réponse à l'ensemble de ces exigences. Avec l'aide des partenaires industriels Fibercryst et Cilas, ils portent sur la réalisation de sources laser compactes et efficaces à fibre cristalline Er3+:YAG directement pompée par une diode laser pour des applications militaires.A l'aide d'un algorithme de simulation d'un laser Er3+:YAG déclenché passivement élaboré et affiné durant la thèse, plusieurs sources sont réalisées expérimentalement. L'étude autour des absorbants saturables pour le déclenchement passif a permis une amélioration notable des caractéristiques du faisceau.Ces recherches, dont les résultats peuvent déjà présenter un certain intérêt commercial, ouvrent la voie vers de nouvelles techniques et architectures autour des sources laser à cristaux dopés aux ions erbium pour la conception de futurs prototypes plus performantsAmong the several applications of laser sources, some requires kilometers range propagation in the atmosphere : telemetry, guidance system or active imagery. High pulse energy improves the range of the system, but may cause permanent blindness to an observer's eyes. Hence, these applications must use laser beam which wavelength are located in the eye-safe region, ideally at the local minimum of the atmosphere absorption (1550-1650 nm). Such laser sources are already commercially available, but are not suited for the demanding military needs : compacity, electrical consumption, performance and large operating temperature range (-40°C/+60°C).My work aims to develop a laser source filling these specifications. Thanks to the collaboration with the industrial partners Fibercryst and Cilas, it focuses on the design of a compact, efficient, directly diode-pumped Er3+:YAG single cristal fiber laser for military applications.With a homemade numerical simulation of a passively Q-switched Er3+:YAG laser source, many laser emitters are experimentally designed and compared. Further studies around saturable absorbers allowed sensible improvements of the output pulse energy.This work, whose results may already be commercially interesting, may lead to new technics and architectures of erbium doped solid-state laser for better prototypes
2
Phelps, Charles Dustin. "Diode-Pumped, 2-Micron, Q-Switched Tm:YAG Microchip Laser". University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1304695817.
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Lu, Min. "Performance of continuously pumped, passively Q-switched, solid state lasers". Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6953/.
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This thesis studies the relationship between the pairs of resonator output coupling and intra-cavity absorber initial transmission, and the FWHM (full width at half maximum) pulse duration of a continuously pumped passively Q-switched solidstate laser, when the output energy is pre-determined. Depending on the magnitude of the pumping power, three different rate equation models are used to evaluate the required output coupler reflectivity and absorber initial-transmission pair for the corresponding FWHM pulse duration. The energy transfer kinetics of the passively Q-switched laser decides the required pumping power; and the pair of output coupler reflectivity absorber transmission pair, determine the build-up time of Q-switching and the repetition rate of the laser system. Hence, the forms of the models are controlled by two conditions: 1) the build-up time of Q-switching; and 2) the recovery time of the absorber. When the build-up time of Q-switching is relatively short, but the recovery time of the absorber is long, Model I is based on the simplified laser rate equations. It is used to evaluate the output coupler reflectivity and absorber initialtransmission pair, which satisfies the pre-determined output energy and FWHM pulse duration. Model II is set up to study the case when both the build-up time of Q-switching and the recovery time of the absorber are long. In Model II, the laser rate equations are solved using the Runge-Kutta method. Model III simulates the case when the recovery time of the absorber is short. To validate the models, the simulation results of practical passively Q-switched laser systems are compared with experimental results reported in the literature. The agreement of the simulation results with reported experimental results demonstrates the importance of the boundary conditions for the different cases, and verifies the soundness of the models. Generalizing the simulation results, obtained from different passively Q-switched laser systems with different pumping power and different pre-determined output energy, yields general conclusions which permit a designer to select the correct parameters for a desired laser performance.
4
Serres, Serres Josep Maria. "Continuous-wave and passively Q-switched solid-state microchip lasers in the near-infrared". Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/460758.
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Aquest treball tracta de la caracterització de làsers compactes d'estat sòlid, amb un primer enfocament, l'estudi del
concepte microxip aplicat al làser en diversos hostes cristal·lins dopats amb terres rares. Es reporta els resultats sobre
l'estudi de l'efecte de thermal lens, necessari per a l'obtenció de làser amb aquesta configuració, així com pel
funcionament làser amb continu i polsat utilitzant la tècnica Q-switch.
En els experiments, el concepte microxip es defineix com una cavitat làser quasi monolítica. Aquest concepte s'estudia
per a diferents emissions de làser a ~1.06 m d'ions Yb3+ i Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hi ha
~2.05 m del Ho3+.
En el règim d'ona contínua s'examina detalladament per als ions de lantànids trivalents esmentats en diversos hostes
cristal·lins amb l'objectiu de comparar el potencial de cada material. En aquest treball, es demostren eficiències molt
properes al límit teòric.
D'altra banda, també es presenten làsers polsats d'estat sòlid amb la configuració microxip amb diversos absorbidors
saturables. Amb aquest propòsit, s'utilitzen com a absorbidors saturables nous nanomaterials com el MoS2, nanoestructures
de carboni (SWCNT, el grafè d'una i de diverses capes) i un SESA. A més, el més convencional Cr:YAG
(~1.06 m) i el Cr:ZnS (~1.9 m) s'examinen per comparar els seus rendiments.Este trabajo trata de la caracterización de láseres compactos de estado sólido, con primer enfoque, el estudio del concepto microchip aplicado al láser en varios huéspedes cristalinos dopados con tierras raras. Se reporta los resultados sobre el estudio del efecto de la thermal lens, necesario para la obtención de láser con esta configuración, así como para el funcionamiento láser en continuo y pulsado utilizando la técnica Q-switch. En los experimentos, el concepto microchip se define como una cavidad láser casi monolítica. Este concepto se estudia para diferentes emisiones de láser a ~1.06 m de los iones Yb3+ y Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hay ~2.05 m del ion Ho3+. En régimen de onda continua se examina detalladamente para los iones de lantánidos trivalentes mencionados en varios huéspedes cristalinos con el objetivo de comparar el potencial de cada material. En este trabajo, se demuestran eficiencias muy cercanas al límite teórico. Por otra parte, también se presentan láseres pulsados de estado sólido con la configuración microchip con varios absorbedores saturables. Con este propósito, se utilizan como absorbedores saturables nuevos nanomateriales como el MoS2, nano-estructuras de carbono (SWCNT, el grafeno de una y de varias capas) y un SESA. Además, el más convencional Cr:YAG (~1.06 m) y el Cr:ZnS (~1.9 m) se examinan para comparar sus rendimientos
This work deals with the characterization of compact solid state lasers, as a first approach to the study of the microchip laser concept applied to several rare earth-doped crystalline hosts. The results on the study of the thermal lens, required for the microchip laser operation as well as the continuous wave and passive Q-switched laser operation in microchip configuration are reported. In the experiments, the microchip concept is defined as a quasi-monolithic laser cavity. Such a concept is studied for different laser emissions at ~1.06 μm from Yb3+ and Nd3+ ions, at ~1.3 μm from Nd3+, at ~1.95 μm from Tm3+ and at ~2.05 μm from Ho3+. The continuous wave regime is examined in detail for the above mentioned trivalent lanthanide ions embedded in several crystalline hosts with the aim to compare the potential of each gain material. Slope efficiencies very close to the theoretical limit are demonstrated in this work. On the other hand, microchip solid state lasers passively Q-switched with several saturable absorbers are also presented. For this purpose, novel nanomaterials such as MoS2, carbon nanostructures (SWCNTs, single- and multilayer graphene) and a SESA are used as saturable absorbers. Besides, the most conventional Cr:YAG (~1.06 μm) and Cr:ZnS (~1.9 μm) are examined to compare their performance.
5
Mercer, Colin. "Development of a Diode Laser Pumped Passively Q-Switched Laser Source for Range-Finding and Designating". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508559.
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Segura, Sarmiento Martha Yamile. "Monoclinic tm:klu(w04)2: a new crystal for efficient diode-pumped continuous-wave and q-switched lasers". Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/80852.
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El doble tungstato cristalino de potasio y lutecio con estructura monoclínica, KLu(WO4)2, se ha establecido como una nueva matriz laser de estado sólido para iones de Tm, Yb y Ho debido a (i) las altas secciones eficaces de absorción y emisión; (ii) la relativamente larga distancia entre iones Lu-Lu permitiendo altos niveles de concentración de iones activos sin perdidas significativas por fluorescencia; y (iii) el tiempo de vida suficientemente largo del nivel emisor de la transición láser asegurando un alto almacenamiento de energía. Estas características son explotadas en este trabajo usando Tm como ion activo para generar emisión láser a 1.94 µm.
El máximo local de absorción del agua a esta longitud de onda hace a este laser interesante para aplicaciones medicas y atmosféricas. Cambio de polarización, operación en dos longitudes de onda, laser vibrónico, diseño láser de capa delgada Thin-disk, Q-conmutado pasivo y la interacción láser-tejido del láser de Tm:KLu(WO4)2 a 1.94 µm son demostrados en este trabajo.Monoclinic potassium lutetium double tungstate KLu(WO4)2 is established as new laser host for Tm, Yb and Ho active ions due to (i) its very high values of absorption and emission cross sections (ii) its relatively large Lu-Lu distances allowing high ion concentration with minimum fluorescence quenching effects and (iii) the long lifetime of the upper laser level ensuring high energy storage. These characteristics are exploited in this work using Tm as active ion to generate laser emission at 1.94 µm. The local maximum of water absorption at this wavelength makes this laser interesting for medical and atmospheric applications. Polarization switching, dual-wavelength operation, vibronic laser, thin-disk laser design, passive Q-switching and the laser-tissue interaction of the 1.94 µm Tm:KLu(WO4)2 laser are demonstrated in this work
7
El, bassri Farid. "Sources lasers déclenchées nanosecondes : Applications à la spectroscopie Raman cohérente sous champ électrique". Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0060/document.
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Du fait de leur compacité, leur robustesse et leur faible coût, les microlasers impulsionnels nanosecondes constituent des sources particulièrement attractives pour de nombreux systèmes de détection et d'analyse, en particulier les cytomètres en flux ou les dispositifs pour la spectroscopie CARS (Coherent Raman Anti Stokes Scattering). Cependant, ces applications nécessitent des performances améliorées en ce qui concerne la gigue temporelle et la cadence de répétition accessible. Dans sa première partie, cette thèse propose des solutions originales pour atteindre les performances requises à partir de microlasers passivement déclenchés, grâce à la mise en oeuvre d'une cavité hybride couplée, pompée par une onde modulée en intensité. Une cadence de répétition supérieure à 30 kHz avec une gigue demeurant inférieure à 200 ns est atteinte. Le potentiel de microlasers à fibres déclenchés par modulation du gain pour monter en cadence est aussi évalué, montrant que des impulsions à faible gigue, à une cadence de plus de 2 MHz peuvent être produites. Enfin, la dernière partie est consacrée à la mise au point et à l'exploitation d'un nouveau système de spectroscopie CARS assisté par une excitation électrique haute tension. Ce dispositif, réalisé à partir d'un microlaser amplifié, permet de s'affranchir du bruit de fond non résonnant des mesures et de réaliser une analyse spectroscopique fine de la réponse de différents milieux d'intérêt sous champ continu ou impulsionnel, pouvant conduire à une nouvelle méthode de microdosimétrie de champ. Diverses applications, dont la granulométrie à l'échelle micro ou nanométrique ou l'identification de marqueurs pour la biologie, sont démontréesThanks to their compactness, robustness and low cost, pulsed nanosecond microlasers are particularly attractive sources for different detection and analysis systems, particularly flow cytometers or devices for CARS (Coherent Anti Raman Stokes Scattering) spectroscopy. However, these applications require reduced time jitter and increased repetition rate. The first part of this thesis proposes novel solutions to achieve the required performance from passively Q-switched microlasers, which are based on an hybrid coupled-cavity and intensitymodulated pump wave. A repetition rate greater than 30 kHz with jitter remaining lower than 200 ns is reached. Pulsed fiber microlasers operating by gain switching are also studied, showing that pulses with low timing jitter, at a repetition rate of more than 2 MHz can be obtained. The last part is devoted to the development and the implementation of a new system of CARS spectroscopy assisted by a high-voltage electrical stimulation. This device, based on an amplified microlaser, allows to substract the non-resonant background noise in the measurements. Thus, a fine spectroscopic analysis of the response of different environments of interest in continuous or pulsed field can be achieved. It may lead to a new method for field microdosimetry. Various applications, including granulometry at the micro or nanometric scale and the identification of markers for biology, are shown
8
Lavastre, Eric. "Déclenchement des microlasers solides émettant à 1,55 µm par un dispositif à semiconducteur". Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10173.
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Les microlasers emettant a 1,55 m sont des lasers solides de faible volume (<1 mm#3) a base de verre : er, yb dont les miroirs de la cavite sont directement deposes sur le milieu a gain. En introduisant un modulateur dans la cavite, il est possible de declencher le laser afin d'obtenir des impulsions de puissance crete elevee donc exploitables pour des applications telles que la telemetrie. L'objet de cette these est d'utiliser un dispositif a semiconducteur comme modulateur. De par leurs proprietes optiques et electriques, les semiconducteurs presentent un fort potentiel pour le declenchement passif et le declenchement actif. Les structures etudiees sont des couches epaisses et des structures a puits quantiques constituees d'in#xga#1##x##yal#yas epitaxiees sur un substrat d'inp. En declenchement passif dans une configuration microlaser, les meilleurs resultats ont ete obtenus avec une couche epaisse de 80 nm d'in#0#,#4#8ga#0#,#5#2as. Les energies et les puissances cretes par impulsion sont respectivement de 2 j et 2w avec un substrat d'inp semi-isolant et, 25 nj et 5w avec un substrat d'inp non dope. Ces differences dans les performances sont dues a des effets non-lineaires associes au substrat d'inp semi-isolant qui elargissent les impulsions. En declenchement actif, les premiers essais en cavite externe ont montre qu'il est possible de moduler l'emission laser en appliquant des creneaux de tension inferieurs a 20v pendant 1 s aux bornes d'une diode p. I. N dont la region intrinseque se compose de 10 puits quantiques d'in#0#,#5#3ga#0#,#4#7as dans des barrieres d'in#0#,#5#2al#0#,#4#8as. Afin d'optimiser l'effet du champ electrique, une structure mesa et une passivation ont ete realisees.
9
Lin, Yao-chun y 林耀群. "Use of GaAs as a passive Q-switch as well as an output coupler for diode-pumped Nd:YVO4 lasers". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/93917818462083697801.
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碩士國防大學中正理工學院
應用物理研究所
94
In this paper, we investigate an all-solid-state passive Q-switched Nd:YVO4 laser system. Q-switching operation is very common and important for diode-pumped solid-state lasers. And in recent years, Q-switched lasers have been used in many fields, such as nonlinear optics, range finding, medicine, and micromachining, etc. In this experiment, we use GaAs wafer as an important element for passive Q-switching. The GaAs wafer, which works as an saturable absorber, was used as the Q-switch in the laser system. Moreover, GaAs wafer also acts as an anti-resonant Fabry-Perot resonantor, so we use it as an output coupler. Its reflectance is 73.5%, and its transmittance is 26.5%. We use two gain media with different lengths. One is 6 mm, and the other is 3 mm. The results of this experiment are as follows: The cavity length is adjustable from 8 mm to 17 mm；the shotest pulse width is 7 ns；its photon lifetime is about 0.33 ns；the highest peak power is 314 W；the highest repetition rate is about 1.7 MHz；its pulse energy is up to 2.2 μJ.
10
Tsai, LingYi y 蔡玲意. "Passively Q-switched intracavity optical parametric oscillator". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/85773595800845068740.
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碩士國立交通大學
電子物理系所
93
Extremely short (1.6 ns) high-peak-power (> 10 kW) pulses of lasers at the eye-safe wavelength region about 1.5 �慆 are obtained by intracavity optical parametric oscillators (OPOs). We demonstrated a compact efficient eye-safe OPO pumped by a diode-pumped passively Q-switched Nd:GdVO4 laser to produce peak powers at 1571 nm higher than 20 kW with pulse widths of 0.7ns . On the other hand, we overcome the instablility in the IOPO by using two-mirror structure .At the same time, we raise the pulse energy to 1.5 times. Due to its stability, we try to apply the two-mirror structure to tune wavelengths by temperature. As a result, we can get the curve slope about 0.4nm/0C. By the way, using Nd:Gd0.7Y0.3VO4 crystals may get 3 times the pulse energy by using Nd:YVO4 crystals and 1.8 times the pulse energy by using Nd:GdVO4 crystals.
11
Huang, Wen-Cheng y 黃文政. "The study of passively Q-switched fiber lasers". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/98537971233131679287.
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博士國立交通大學
電子物理系所
102
The double-cladding Yb-doped fiber as the gain medium and the passively Q-switching technique have been utilized in study of high power and high-repetition rate fiber lasers. First we use the double-cladding fiber with core diameter of 30 μm, and the AlGaInAs semiconductor material and the Cr4+:YAG crystal are used as the saturable absorbers (SA) respectively. By using the AlGaInAs as the SA, pulse energy up to 0.45 mJ with the repetition rate of 30 kHz in the pump power of 24 W can be attained. With the Cr4+:YAG crystal as the SA, we can have the laser output with a pulse energy of 0.35 mJ at the pulse repetition rate of 38 kHz in the same pump power. We also have comparative studies between these two SAs. For scaling energy further, the photonic crystal fiber (PCF) with the core diameter of up to 70 μm is used as the gain medium. With the AlGaInAs as the SA, the pulse energy is significantly increased 2.4 times to 1.1 mJ, and the shorter cavity length results in the pulse width reducing from 60 ns to 10ns. As a sequence, the peak power is boosted up from 7.5 kW to 110 kW. This scheme is also used for pumping the extracavity optical parametric oscillator (OPO), and the output energy of 138 μJ with the repetition rate of 6.5 kHz at the wavelength which can be tunable from 1513 nm to 1593 nm is obtained. By employing the Cr4+:YAG SA, the pulse energy also has almost 2-times enhancement to 0.63 mJ and the pulse width decreases from 70 ns to 36 ns. An intracavity OPO was demonstrated based on this scheme, output power of 0.47 W at 1515 nm was obtained. To achieve higher peak power, it is necessary to have smaller pulse width, so we adopt the configuration of master oscillator fiber amplifier (MOFA). By using a Nd:YVO4/ Cr4+:YAG passively Q-switching laser as the seed laser and a 30-μm-core double-cladding fiber as the amplifier, the amplifier can generate pules with energy of 0.192 mJ at the repetition rate of 25 kHz and the pulse width is down to 1.6 ns. In addition, a PCF MOFA was used to pump the extracavity nonlinear wavelength conversions module, output powers of 1.7 W of the second harmonic generation at 532 nm and 1.1 W of the third harmonic generation at 355 nm were realized at the fundamental pump power of 3.3 W.
12
Tsai, Ming-Chen y 蔡明辰. "Investigation of orthogonally-polarized passively Q-switched lasers". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4fayr5.
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碩士國立交通大學
電子物理系所
106
The aim of this thesis is to study the influences of birefringence effect of gain crystal on the output polarization states for the passively Q-switched (PQS) orthogonally polarized lasers. Considering the stress-induced birefringence to the isotropic gain crystals, we firstly compared the temporal dynamics of the orthogonally polarized pulse trains of the Nd:YAG and c-cut Nd:YVO4 PQS lasers . Experimental results reveal that the two orthogonally polarized states of the Nd:YAG PQS laser will exhibit regular energy switching behavior in the pulse trains, whereas the pulse trains of the c-cut Nd:YVO4 laser present comparatively random switching dynamics between the orthogonally polarized states. In order to further explore the switching behavior of the orthogonally polarized states in the PQS pulse trains under different levels of the stress-induced birefringence, the temporal dynamics of a monolithic Nd:YAG/Cr4+:YAG PQS laser was studied considering different pumping conditions. Experimental observations show that the period corresponding to the polarization switching in the PQS pulse trains is highly correlated with ratio of the lasing longitudinal mode numbers for the orthogonally polarized components. We expect the experimental finding can be applied to the realms of optical remote sensing and optical communication and so forth.
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Kun-GueiHong y 洪崑貴. "Dynamic behavior in the passive Q-switched Nd:YVO4 laser on pumping modulation". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/68080196281387953459.
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碩士國立成功大學
光電科學與工程學系
100
n this thesis, we study that the nonlinear dynamical behavior in passively Q-switched Nd:YVO4 laser. With increasing the modulation frequency of pumping source, the behavior of the pulse train in sequence will occur: period two, period three, period one and finally chaotic dynamics phenomena with some path of development. At the same time when the modulation frequency was closed to the pulse repetition frequency, the timing jitter of pulse train became very stable, and the pulse width compared with pulse train without modulation was compressed. In simulation, we modulated gain with sine wave. All the dynamic behavior of the pulse train of simulation corresponded with experiment. It’s easy to analyze that some pulses of the pulse train have stronger excitation and become the stronger peak intensity, and some pulses become weaker one because of small excitation. This phenomena lead to be period two signal. So does the period three, and so dose chaotic pulse train. The Q-switched pulse laser system can be controlled into special condition by gain-modulation with some special frequency.
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Fan, Shin-An y 范信安. "Study of All Fiber Passively Q-Switched Pulses Laser". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/18202805653536288799.
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碩士中原大學
應用物理研究所
95
An all-fiber passive Q-switched pulsed laser has been established and its performance has been investigated. The laser system was configured by using a Samarium (Sm)-doped fiber as saturable absorber, a Yb3+-doped double cladding fiber as the gain medium, and a Bragg-fiber gratings as the optical cavity. In the past, most of the Q-switched fiber lasers are consist of bulky elements that normally invoke sophisticated designs and are usually drawback by incompactness. Here, the conventional crystal saturable absorber was replaced by a Sm-doped fiber, making this pulsed laser as a genuine all-fiber Q-switched laser. In addition, a Yb3+-doped double cladding fiber was also adopted in the system to improve its coupling efficiency and output power. In the preliminary test, a pulse energy of 202 nJ, repetition rate of 50 kHz have been shown. The present optimized results, the pulse width of 0.9μs, and with a peak power of 224.4 mW at center wavelength of 1086.44 nm and a FWHM bandwidth of 1 nm were achieved. The effects of pumping optical source power on the output power, repetition rate, and pulse energy were also investigated. It was found that the higher the pumping power, the higher the output power and pulse energy, but the lower the repetition rate.
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Chen, Li-Hsuan y 陳立宣. "The study of passively Q-switched Yb:YAG ring laser". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/16847395367843408048.
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碩士國立中山大學
光電工程研究所
94
Compared with Nd:YAG, the traditional high power solid state laser gain medium, Yb:YAG has less quantum defect, no excited state absorption, and longer fluorescence lifetime, which makes it suitable for Q-switched laser. In addition, concentration quenching is absent in Yb:YAG, higher concentration of active ion makes the thickness of gain medium thinner. For ring cavities, the necessity of symmetrical beam path is important, a thinner Yb:YAG crystal can reduce the shift of optical beam path and avoids cavity unstability. Thus, Yb:YAG is suitable for the two-mirror ring cavity. In this study, a compact and efficient Yb:YAG ring laser with 50.3% slope efficiency was demonstrated. And the Yb:YAG ring laser performances influenced by thermal effect was analyzed and compared to that of Nd:YAG ring laser. The polarization of ring lasers with different configurations were also discussed. In manufacturing process, the coating design on gain medium and laser mirrors were introduced. The advantages of passively Q-switched laser are efficient, compact, simple setup and no complicated driving circuits. They make passively Q-switched laser suitable for various applications, such as nonlinear optics, medical treatment, micromachining, material processing, and range finder. Due to spontaneous noise from the gain medium, conventional passively Q-switched laser has large timing jitter. This study is to build up a passively Q-switched Yb:YAG/Cr4+:YAG ring laser with lower timing jitter. At present, a Q-switched ring laser with a peak power of 208 W and a pulse width of 33 ns, was developed. Its slope efficiency is 18.1% with a timing jitter of 11.9%. To our knowledge, this is the first passively Q-switched Yb:YAG/Cr4+:YAG ring laser.
16
Weng, Yi-Lung y 翁義龍. "Intracavity Frequency-Doubled and Passively Q-Switched Blue Laser". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/71879682231142160516.
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碩士國立中山大學
光電工程研究所
88
The purpose of this study is to develop a solid-state blue laser which has advantages of high power, short wavelength, and compact. It can be applied in micromaching, LIDAR, underwater ranging, biochemical techniques, and so forth. We increased the peak power of the laser effectively by a low-cost, small, and easy-use passive Q-switching technique. In addition, intracavity frequency-doubling is an economic way to achieve non-linear frequency conversion for blue generation. By integrating of these two techniques, we develop a compact all solid-state high-power blue laser with 83 W peak power at 473 nm. Restricted to reabsorption loss, the optical to optical conversion efficiency of 4F3/2 → 4I9/2 quasi-three-level laser is lower than 4F3/2 → 4I11/2 four-level laser for Nd:YAG crystal. The reabsorption loss will change with the temperature variation of the gain medium, it enormously affects to the performance and stability of quasi-three-level lasers. Therefore, in addition to make systematic studies of the conversion efficiency of KNbO3, BBO, LBO as the intracavity SHG crystals for generation of high-power blue laser, we use the numerical analysis to investigate the influence of reabsorption loss to quasi-three-level passive Q-switching laser. At present, blue laser with peak power of 83 W and pulse width of 10.6 ns was generated as a result. To our knowledge, the compact all solid-state high-power pulsed blue laser is demonstrated for the first time by integrating of passive Q-switching and intracavity frequency-doubling simultaneously.
17
Chen, Se-Jie y 陳世杰. "Study of Passive and Active Q-Switched Intracavity Frequency-Doubled Solid State Laser". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/64496007136987231739.
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碩士義守大學
電機工程學系
92
We have finished the theoretical analysis of active/passive Q-switched intracavity frequency doubled solid state laser without any sponsor or experimental equipments. With the analysis of plane E-M wave, the results of our model show that for a small compact laser cavity operating in TEM00 mode with single frequency output, the laser output energy and peak power will be greatly affected by both the ETU effect [15] caused by high pumping power and different ratio of pumping mode to laser mode. We also incorporate the pulse repetition frequency (PRF) [31,32] into the rate equation. Compared with experimental data, our theoretical predictions show great agreement with the experimental results of J. Liu [19]. Besides, the results show that the ETU effect are seriously increasing under the conditions of high pumping power and low PRF. We also study the passive saturable absorabler (SA) Q-switched laser. A second threshold condition [54] for intracavity double frequency is derived. However, the second threshold condition is not related to the second harmonic generation (SHG) crystal. We also use Lagrange multiplier method to obtain the optimal energy of intracavity SHG of Q-switched laser [53]. We hope some experiments can be set up to verify our predictions. In the near future, we will continue working on how to apply the second threshold condition to simplify the design of laser for optimal energy.
18
Su, Huan-Rui y 蘇桓銳. "Q-switched mode locking of Nd:YAG lasers by hybrid active and passive mechanisms". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/33598935719840420612.
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碩士東海大學
物理學系
99
This thesis studies Q-switched mode locking of Nd:YAG lasers by using active mode-locked technique in combination of gain switched or passive Q-switched technique. In the gain-switched experiment, Q-switched mode-locked pulses were observed when the modulation frequency tuned to resonate with natural frequency of the laser system. A four to five times enhancement of peak power and an improvement of mode-locked performance can be obtained by applying active mode locking to the gain-switched experiment. In passive Q-switched experiment, we have also observed Q-switched mode-locked pulses. The conditions for generating Q-switched pulses by optimizing average output power, repetition rate, and peak power were studied. In these cases, Q-switched pulses with average output power as high as 12 mW, repetition rate up to 20 KHz, and pulse width as low as 200 ns were obtained. By applying active mode locking to passive Q-switched experiment, the mode-locked performance improvement together with a three times increment of peak power could also be achieved.
19
Lin, Yung-Hsiang y 林泳詳. "Study of Passively Q-switched Lasers with Volume Bragg Grating". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/62045743617257417877.
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碩士國立清華大學
光電工程研究所
96
In this thesis, the theory of Passively Q-witched Laser will be discussed in detail. A Volume Bragg Grating (VBG) was used to eliminate longitudinal mode in cavity. The gain medium was Nd:GdVO4 with 1% Nd doped and the saturable absorber was Cr:YAG. There were four laser systems finished step by step including (1) CW laser generation with linear cavity (2) passively Q-switched laser generation with linear cavity (3) CW laser generation with V-type cavity (4) passively Q-switched generation with V-type cavity. VBG was used in the third and the fourth system to compare with the first and the second system which without VBG. Another saturable absorber Cr:YVO4 was used to try to build a passively Q-switched laser.
20
Te-LunYen y 顏德倫. "Study on 1590-nm passively Q-switched all-fiber laser". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/m9ww3x.
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Chang-ChingTsai y 蔡長青. "Passively Q-switched all-fiber laser at high peak power". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/54336188897487780061.
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碩士國立成功大學
微電子工程研究所
104
This thesis focused on simulation of Q-switched pulsed laser and implement the passively all- Yb+3fiber Q-switched pulsed laser at high peak power using mode-field area mismatch method in dual cavity. Since the output power of single-mode laser diode is too low，we use multi-mode laser and cladding pumped laser system to boost the output power of laser system and achieve the high power Q-switched all-fiber laser system. We also derive some theories about mode-field mismatch method and rate equations about dual cavity. Based on the outcome in the chapter2，we establish a numerical model to simulate a Q-switched pulse. In the simulation，we get a Q-switched pulse with an energy of 38.64 μJ、a width of 32.83 ns and a peak power of 975W. Moreover, the performance of pulses can be improved by replacing the longer SAQS fiber in the experiment. The tendency observed in the experiment provide a clear direction to optimize the pulsed laser system in the future.
22
Yang, Yeon-Lung y 楊永隆. "Resonator-Configuration-Dependent Dynamics of Passively Q-Switched Nd:YAG Lasers". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/94664830333313182216.
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碩士東海大學
物理學系
92
In this thesis, we experimentally study the resonator-configuration dependent dynamics in an axially pumped passively Q-switched Nd:YAG laser with a plane-concave cavity. We observed the average output power, repetition rate and pulse width as a function of the cavity length at different pump power. Our investigation shows that the laser pulse train will fall into unstable when the cavity length is adjusted near the edge of the geometric stable resonator configuration. We also find that the laser tends to run into multiple transverse modes in this region. Therefore,the instability of Q-switched pulses is related to the interaction of multiple transverse modes around the hemispherical resonator configuration where they are subject to a significant cavity-length-dependent variation of gain or loss.
23
Tu, King-Chao y 杜金潮. "Chaos in a Passive Q-Switched Nd：YAG Laser with a Cr4+：YAG Saturable Absorber". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/35974082860855292093.
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碩士逢甲大學
光電物理研究所
91
The character of a passive Q-switched Nd:YAG laser system with a Cr4+:YAG saturable absorber is studied. The pulse has 1.8 kW peak power and 20 ns duration with a repetition rate of 5 kHz as the pump power being 2.8 W. When we increase the pump power, the period doubling route to chaos is found. A general period doubling route begins from period 1, but we had observed the period doubling route beginning from period 3. Besides, period 5 was also obtained in the experiments.
24
Chou, Hsin-Yao y 周妡遙. "Multi-wavelength passive Q-switched Er-doped fiber laser with a semiconductor saturable absorber". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/mc439b.
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碩士國立交通大學
光電工程研究所
106
In this thesis study, we build a passive Q-switched E-doped fiber laser with a semiconductor saturable absorber. The laser constitutes of 2.89 m SMF-28, 0.7 m Er-doped fiber, and 2 m high nonlinearity fiber. By adjusting the two polarization controllers inside the cavity as well as the 980 nm laser diode pump power, we can let laser operate under two different Q-switched states: single-wavelength state and multi-wavelength state. We have experimentally investigated the lasing characteristics of the multi-wavelength Q-switched state and find an interesting energy exchange oscillation phenomenon between the pulse amplitudes of different wavelengths.
25
Dong-LinLi y 李東霖. "Radial and azimuthal polarizations in passively Q-switched solid-state laser". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/73158684348863903295.
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碩士國立成功大學
光電科學與工程學系
101
Radially and azimuthally polarized beams were generated in passively Q-switched Nd:GdVO4 laser with a Cr:YAG saturable absorber. Based on the cavity design, the cavity configuration simultaneously satisfied the thereshold of the passive Q-switching and the generating condition of the cylindrical vector beam. When the pump power was 5W, the pulse width, repetition frequency, and the average power were 110 ns, 12.3 kHz, and 270 mW, respectively. The pulse operation had better polarization ratio than that of continuous-wave operation. Moreover, the spatial-dependent pulse trains were explored, and the dynamical behavior is an interesting future work.
26
Huai-MinHuang y 黃懷民. "Full-band passively Q- and gain-switched Yb3+ all-fiber laser". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/99486101101667485629.
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碩士國立成功大學
微電子工程研究所碩博士班
98
The purpose of the study is to produce a passively pulsed Yb3+ all-fiber laser that self-balances between being Q-switched at 0.97-0.98 μm and being gain-switched at 1-1.12 μm, using a continuous-wave 915 nm pump laser diode. The device was experimentally demonstrated at 976 nm of Q-switching, and 1064 nm of gain switching. With pump power of 110 mW, a single-mode Q-switched pulse at 976 nm with pulse energy of 1.5 μJ and pulse duration of 275 ns was achieved. Furthermore, the rate equations to simulate the interactions between the dual-wavelength photons and the populations of the ytterbium gain and absorber fibers were established. With desirable fiber Bragg gratings, a CW-pumped Yb3+ laser can produce sequential pulses in the ytterbium emission band of 0.97-1.12 μm.
27
Liao, Chien-Hsun y 廖建勛. "Pump and cavity effects in a passively Q-switched Nd:YVO4 lasers". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/23300563772634102279.
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碩士東海大學
物理學系
96
In this thesis, we experimentally study pump and cavity effects in passive Q switching of diode-pumped a-cut and c-cut Nd:YVO4 lasers. The average output power, pulse width, and period were measured as functions of the pump spot size and resonator configuration. Our investigation shows that larger pump spot size is favorable for good Q switching. Suppression and enhancement effects on passive Q switching were observed near the border of geometrically stable resonator figuration. We also find that c-cut Nd:YVO4 crystal is a more preferable gain medium than a-cut one for generating short pulse width, high peak power, and stable Q-switched pulses. Based on these studies, the generation of Q-switched pulses with pulse width as short as 26 ns and peak power up to 150 W were achieved by use of a c-cut Nd:YVO4 crystal under pump power of 890mW.
28
Madlala, Bigboy. "Designing a low cost passively Q-switched solid state laser transmitter". Thesis, 2017. https://hdl.handle.net/10539/24990.
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A dissertation submitted to the Faculty Of Science in partial fulfilment of the
requirements for the degree of
Master of Science by research only
in the School of Physics, University of the Witwatersrand, Johannesburg. July 11, 2017.A discrete Q-switched laser that gives a side-lobed single pulse as a laser output was implemented; followed by studying energy extraction e ciencies and pulse characterisation. The aim was to help design a passively Q-switched laser that gives a smooth single pulse of optimum energy as a laser output. The smoothness feature in a single pulse is important in some applications such as range nding. The concepts are demonstrated both experimentally and numerically; the latter using Fox-Li approach to modeling resonator modes with the Fresnel's integral for the system under study. In the rst two chapters, fundamentals of how a laser works and the spatial mode development are studied. In chapter 1, the principles of a laser are discussed: absorption, spontaneous and stimulated emission. Also, di erent types of pumping sources and resonator con gurations that can be used are discussed. In chapter 2, the focus is on developing spatial modes of a laser. The fundamental and high order modes are discussed together with their propagation laws. Then a numerical method is used to nd the eigenmodes of an arbitrary resonator con guration. This numerical method is used to simulate propagation of a fundamental mode and the simulation results are compared to analytical propagation laws. Then, this numerical method is used to simulate a laser resonator. The eigenmode of the lowest loss in the resonator was found. In chapters 3 and 4, experimental work is done on a Q-switched laser where the focus is on the overall laser performance. In chapter 3, Q-switched laser output energies are studied for di erent combinations of Q-switch transmission values and output coupler re ectivities. In addition, the in uence of spatial modes on a Q-switched pulse shape and pulse width are studied, taking into account beam divergence. In chapter 4, conclusions and future work are presented. In future work, the knowledge of spatial mode in uence on pulse shape, pulse width and beam divergence from chapter 3 is exploited. Then particular resonator con guration that gives optimised output results (Q-switched laser output energy, beam divergence, pulse shape and pulse width) is chosen. On that particular resonator, di erent Q-switch transmission values are studied, but now looking only at beam divergence and pulse width. Also, some suggestions on further improving laser performance are given.
LG2018
29
Tsung-Yuan, Tsui y 崔宗元. "The Study of the Passively Q-Switched Nd:YAG/Cr4+:YAG Laser". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/56366526211591825702.
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碩士國立中山大學
光電工程學研究所
86
Passively Q-switched laser is the most simple and economic one in all kinds of Q-switched lasers. Dye has been used in passively Q-switched laser as satur-able absorber, but bleaching and deterioration make it trouble for frequent re-placing, and there is no way for direct control of the pulse repetition rate.T- iming jitter is a serious problem for this type of laser. In this thesis, a diode-laser-longitudinally pumped Nd:YAG/Cr4+:YAG Q-swi-tched laser is studied. Cr4+:YAG is a good saturable absorber for passively Q-switched laser because of its good material quality and high damage threshold(500MW/cm2).We tried 2 different laser cavity structures for this kind of laser, half-symmetry and miniature. For the half-symmetry laser cavity, the best re-sults we achieved for pulse width, peak power and pulse energy are about 15 ns,11.4 KW and 0.2 mJ respectively; and for the other one, they are 4 ns, 21 KW and 0.091 mJ. To the best of our knowledge, pulse energy for both laser cavity are the largest for longitudinally diode pumped Nd:YAG/Cr4+:YAG laser. Timing jitter is a very serious problem in a passively Q-switched laser. Alot of theoretical works have been done on the optimization of the peak power and pulse width. In this thesis, a model is constructed for analyzing this pro-blem numerically. In the experiment, 41% timing jitter improvement on half-sym-metric laser cavity is done by external modulation on Cr4+:YAG using a laser d-iode.
30
Chen, Yi-chun y 陳怡君. "Spatial and temporal behavior in diode-pumped passively Q-switched laser". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/8t4y2h.
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碩士國立交通大學
電子物理系所
92
We can obtain high peak power laser with absorber inside cavity. High peak power lasers are applied to distance measuring, radar, medical system and industry marker process. The lasers which are used to be the distance measuring tools has a series pulse delay problem. In our thesis, we will discuss that the transverse modes of different cavities and the variation of pulse delays of different mode position. Delay in pulse arrival times from hundreds of picoseconds to several tens of nanoseconds can be observed in our experiment.
31
Lee, Jian Lung y 李建龍. "Aanlysis of passively Q-Switch Lasers With Simultaneous Mode-Locking : Nd : YAG / Cr4+ : YAG Laser System". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/75762314800730621803.
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碩士國立交通大學
電子物理系
90
We can obtain high peak power laser with absorber inside cavity. High peak power lasers are applied to distance measuring, radar, medical system and industry marker process. Increasing the length of cavity leads to narrower pulsewidth and higher peak power of pulse laser. A general recurrence is derived for the analysis of temporal shape of a single Q-switch envelope with mode-locked pulse trains. With the developed model, the mode-locked pulse and Q-switch pulse energy can be calculated. Excellent agreement was found between the present results and detailed theoretical computations.
32
Lee, Yin-Wen y 李穎玟. "Output Power Maximization of a Diode Pumped Passively Q-Switched Microchip Laser". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/86971500869292581560.
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碩士國立清華大學
電機工程學系
88
Optical characteristics of the laser gain medium, saturable absorber and reflectivity of the output coupler mirror determine the output performance of a passively Q-switched microchip laser. However, the conventional method of enhancing the peak power, in which the pulse width is narrowed by shortening the cavity length, has a complex chip fabrication process. Therefore, this thesis presents a novel means of increasing the peak power of a diode pumped passively Q-switched microchip laser with a fixed cavity configuration. The thermal focusing theory indicates that the laser mode size is enhanced by increasing the pump size and, simultaneously, increasing the peak power. Experimental results indicate that the proposed method enhances the pulse energy by 50% while simultaneously increasing the pump size by 50%, thereby increasing the output peak power under a fixed cavity configuration proportionally. Results in this study demonstrate that the proposed method optimizes the output peak power of a diode pumped passively Q-switched microchip laser without relying on a complex chip fabrication process. Furthermore, a compactly tunable visible laser is demonstrated by combing a monolithic PPLN and the passively Q-switched microchip laser, demonstrated herein.
33
Ching-YuWeng y 翁經宇. "Passive self-balanced Q-and gain-switched erbium all-fiber laser at S and L bands". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/67600113246427107592.
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Pan, Lei. "Experiment and modeling of passively Q-switched ytterbium doped double-clad fiber lasers". Phd thesis, 2010. http://hdl.handle.net/10048/1360.
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High power passively Q-switched fiber lasers have been demonstrated with different ytterbium doped double-clad fibers by using Cr4+:YAG saturable absorber. With small (5.4 m) and medium (10 m) core fibers, single mode
outputs have been obtained with pulse energy of tens of J, pulse duration of the order of a hundred nanoseconds and pulse-repetition-rate of up to 300 kHz. A theoretical model is developed to predict the laser spectrum and numerically
simulate the output characteristics versus pump power. The focused beam in the Cr4+:YAG crystal is assumed to have a Gaussian profile and is analyzed using traveling wave rate equations. The effect of amplified spontaneous emission
is also investigated in the simulation, which shows reasonable agreement with experimental observations. With large-mode-area (25 m) polarization maintaining ytterbium doped fiber, the Q-switched output shows stimulated
Brillouin scattering. Linearly polarized output with >300 kW peak power and a pulse duration as short as 490 ps have been obtained. A theoretical model is developed to simulate passive Q-switching with the stimulated Brillouin
scattering, which shows good agreement with the experiment.
A high power two-wavelength passively Q-switched Yb doped fiber laser has been achieved with a very simple cavity configuration. Single transverse mode output at 1040 nm and 1070 nm was obtained with tens of J pulse energies and hundred nanosecond pulse durations. Modeling of the transient build up of the free-running laser shows the two-wavelength behavior can be attributed to the existence of two gain peaks of Yb-doped fiber under intermediate
pump conditions. A theoretical simulation model qualitatively explains the dynamics of the two-wavelength Q-switching behavior observed in the experiment
indicating that longer fibers and higher pump powers favor 1070 nm laser output and reproduces the pulse pattern where two wavelength pulses alternate at an intermediate pump power.
A compact, adjustment free self Q-switched ytterbium doped fiber laser has been demonstrated with fiber ring mirror, in which cooperative Rayleigh-Brillouin scattering was employed as a gain switching mechanism. As short
as 600 ps pulses have been obtained at both stimulated Brillouin and Raman frequencies, with peak powers estimated to be up to 26 kW and 5 kW, respectively.Photonics and Plasmas
35
Li, Wei-Lun y 李瑋倫. "Investigation of Nd:YLF laser crystal on continuous-wave and passively Q-switched performance". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31613356958999169742.
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碩士國立交通大學
理學院應用科技學程
99
This thesis is aimed to investigate the continuous-wave (CW) and passively Q-switched (PQS) laser performance of the a-cut Nd:YLF gain medium with the wedged angle of 0˚ and 3˚, respectively. Since the Nd:YLF crystal has two emission wavelengths which are π-polarization (1047nm) and σ-polarization (1053nm) in 4F3/2 → 4I11/2, it is practically important to select pure π-polarization (1047nm) and pure σ-polarization (1053nm) independently. Although the wavelength-selection can be achieved with additional components in the laser cavity, this would inevitably lead to unnecessary loss. As a result, we decide to select pure π-polarization (1047nm) and pure σ-polarization (1053nm) simply by tilting the output coupler in this work. In CW laser configuration, we employ the Nd:YLF crystals with 0o-wedged and 3o-wedged as gain medium, and make a thorough study on the performance of π-polarization (1047nm) and σ-polarization (1053nm), respectively. Compare with the results obtained from 0o-wedged one, using 3o-wedged Nd:YLF can more efficiently select two wavelengths and obtain better beam quality in σ-polarization (1053nm). In PQS laser configuration, we utilize the Cr4+:YAG (T0=80%, 95%) saturable absorber to comparative study the PQS performance between π-polarization (1047nm) and σ-polarization in 3o-wedged Nd:YLF crystal. We discuss the influence of initial transmission of Cr4+:YAG and reflectance of output coupler (OC). Experimental results reveal that there is optimal reflectance of OC which generates highest output power for different combinations of the initial transmissions of Cr4+:YAG and lasing wavelengths. The results also show that with increasing initial transmissions of Cr4+:YAG, average output power, pulse repetition rate and pulse width would increase, but pulse energy, peak power would decrease. This means that when designing a laser cavity, we should take these characteristics into consideration so that the performance would meet our demand. More importantly, we find that pulse-to-pulse amplitude stability at σ-polarization (1053nm) is considerably superior than that at π-polarization (1047nm) in PQS laser.
36
Shyu, Shaw-Wen y 徐紹文. "Design and Operation of a Passively Q-Switched, Single-Mode Nd:YAG Ring Laser". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/08668358905349111785.
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碩士淡江大學
物理學系
87
We developed a flash-lamp-pumped saturable-absorber (SA, LiF:F2-) Q-switched single-longitudinal-mode Nd:YAG ring laser with optical feedback, in which one of the two output beams was partially reflected as the feedback. The pulse forming dynamics within the laser cavity and the features of laser operation are the points of our investigation. Because of optical feedback, the counter propagating fields within the ring cavity may influence each other significantly in the course of pulse development. Since the operation of this type of lasers is closely related to the coupling and competition of the counter propagating fields, the system performance may be optimized by varying the reflectivity of the feedback mirror and the output coupler. Theoretically, we designed a model to simulate the operation of the SA Q-switched ring laser: we derived a set of coupled differential equations to describe how the cavity photon numbers, populations of relevant quantum states, and saturable absorption coefficient may vary with time; thereafter, numerical calculation was performed by assuming different operation conditions so as to understand the underlying physics. In the experimental part, we set up a ring laser with a rectangular cavity. The characteristics of the output beams were studied by varying the reflectivity of the feedback mirror (between 4% and 98%) and of the output coupler (8% or 39%), respectively. The pulse-energy ratio of the two output was found to be very big (from about 50 to over 6000). It is noticed that we may still get very stable single-mode output with a pulse duration of about 14 ns even when significant changes in the feedback and pumping voltage are introduced. In comparison with experiment, our theoretical simulation shows very good agreement.
37
Xing-WeiLiao y 廖興維. "A study and improvement of a passively Q-switched all-fiber laser at 976nm". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ws7rd9.
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碩士國立成功大學
微電子工程研究所
105
In this paper, the previous results of the laboratory are studied to study the characteristics of ytterbium-saturated, passive, all-fiber pulsed laser systems. A 915 nm laser diode was used as the driving source for the continuous wave laser and the dual resonator system was set at 976 nm and 1030 nm. At the same time, the modal field mismatch technique is used to accelerate the self-balancing mechanism of saturated absorber, and the all-fiber laser system is set up. In addition, the use of Matlab simulation of the laser equation, auxiliary simulation of the resonant cavity of the behavior. The influence of the parameters on the Ng value and the Na value is discussed, and an optimized result is obtained in the system. Experiments is divided into two parts: (1) by reducing the resonant cavity length to measure the better pulse characteristics and (2) the use of FBG to restore the original structure of the energy reuse, improve system efficiency, while both stable laser diode wavelength The function is equivalent to the third resonator of the system. When the input power is 197mW, it can generate 976nm laser with pulse energy of 0.3574μJ, repetition rate of 101kHz, pulse width of 72ns and pulse peak of 4.963W.
38
Chang, Chuan-Ching y 張專慶. "Study of Self-Mode-Locked Lasers and Passively Q-Switched Lasers with Nd:YVO4 Crystals". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/fk6789.
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博士國立交通大學
電子物理系所
106
Because of the advantages of high absorption coefficients and moderate thermal conductivities, the Nd:YVO4 crystal has been confirmed to be a promising gain medium for solid-state systems to achieve good self-mode-locked (SML) and passively Q-switched (PQS) lasers effectively. To further improve the performance of output efficiency and temporal stability, the physics of the SML and PQS operation in the Nd:YVO4 lasers is deeply studied in this thesis. At the beginning, a thermally insensitive resonator is designed to explore the influence of longitudinal mode spacing on the stability of Nd:YVO4 SML lasers. It is found that a shorter cavity length can lead to larger mode spacing to prevent mode competition for realizing stable SML operation. According to this finding, the output performance of the Nd:YVO4 lasers with monolithic cavities is further investigated. By exploiting the concurrent effect of the SML and self-Raman process of the Nd:YVO4 crystal, the frequency comb expansion of the longitudinal modes is achieved to generate stable mode-locked pulses with the pulse duration of few picoseconds. On the other hand, a concave-convex linear resonator is designed to explore the criterion for achieving a good PQS Nd:YVO4 laser. With the larger effective mode volume, the Nd:YVO4 laser with the designed cavity can easily realize large-pulse-energy and high-peak-power PQS operation with stable pulse trains and excellent beam quality. In addition to investigate the temporal dynamics of the Nd:YVO4 laser, the intrinsic birefringence and large gain of the Nd:YVO4 crystal is further utilized to generate a variety of structured beams in spatial domain. By employing the astigmatic beam transformation, various high-power structured transverse modes are converted into optical vortex beam with large angular momentum for practical applications.
39
Feng, Ying-Wan y 馮嫈菀. "Investigation of orthogonally polarized passively Q-switched monolithic diffusion-bonded Nd:YAG/Cr4+:YAG laser". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/46x43g.
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碩士國立交通大學
理學院應用科技學程
106
The aim of this thesis is to study the relationship between orthogonal polarization and laser longitudinal modes in passively Q-switched (PQS) lasers. First, we change the crystal from isotropic into anisotropic by applying mechanical stress, and compare the temporal dynamics and spectrum in monolithic diffusion-bonded Nd:YAG/Cr4+:YAG PQS laser. Experimental results reveal that the period between two orthogonal polarizations in PQS laser is correlated with ratio of the lasing longitudinal mode numbers and we can realize multi-longitudinal-mode operation. We successfully established single longitudinal mode laser in each polarization by decreasing the length of Nd:YAG/Cr4+:YAG crystal. We expect the experimental finding can be applied in precision measurement and optical communication and so forth.
40
En-SzuOu y 歐恩賜. "Establishment and Evaluation of a LIDAR system with a passively Q-switched fiber laser". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/9nq2b3.
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Wang, Shi-Wei y 王世偉. "Systematic observation of passively Q-switched Nd：YVO4 laser with Cr：YAG as a saturable absorber". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/bm593f.
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碩士國立交通大學
照明與能源光電研究所
108
In this study, a systematic observation of a passively Q-switched Nd：YVO4 laser by varying initial transmission of saturable absorbers and reflectance of output couplers. When the reflectivity of the output coupling mirror is 70% and the initial transmission of Cr：YAG is 67%, the laser performance such as the pulse energy, pulse width, and peak power are 4.38μJ, 6.65ns, and 659.1W, respectively. The rate equations of passive Q-switched laser are used to simulation the influence between the reflectance of output mirror and laser properties.
42
Yueh-chengTsai y 蔡岳呈. "Study on passively Q- and gain-switched all-fiber laser at high repetition rates". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/33655040535263460603.
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碩士國立成功大學
微電子工程研究所
104
This thesis focused on repetition rate of the Q-switched laser. We have used a mode-filed-area (MFA) mismatch method, setting a passively all-fiber erbium Q-switched laser with Er3+ fiber as a SAQS. But the lifetime of Er3+ SAQS is too long to relax the absorption population, and that causes incompletely self-Q-switching mechanism. So we designed a dual-cavity laser structure, which could ignore the SAQS relaxation lifetime and been able to acquire a high repetition rates laser by high power pump. Using this dual-cavity laser structure with multi-mode light sources and double-cladding fibers, we demonstrated a self-balanced Q- and gain- switched cladding pumping laser. The pulses repetition rate achieved about 100k Hz with a pump power of 8.38W. And then we analyzed the variation of the output repetition, pulse duration, peak power and pulse energy with different initiation absorption of SAQS and FBG reflectivity. Finally, simulating the self-balancing mechanism and output laser characteristics by Q-switched rate equations helps us to prove the experimental results.
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Wang, Chien Hung y 王健鴻. "The Study of the Passively Q-Switched Nd:YAG/Cr4+:YAG Laser with External Modulation". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/30600988871297783396.
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碩士國立中山大學
光電工程研究所
87
The timing jitter is a very serious problem in a passively Q-switched laser. However, most of the work of passively Q-switched laser concentrated on the shortening the pulsewidth, increasing the pulse energy or peak power. Little work has been done on the timing jitter for a passively Q-switched laser. In this study, a theoretical simulation is provided to explain the timing jitter and a new method is proposed to improve this problem. Our simulation result indicated that the spontaneous noise in the microwatt range significantly affects the repetition rate of passively Q-switched laser and creates large timing jitter. The phase of modulation signal is also found to be a crucial factor for reducing the timing jitter and can be improved up to 92%. A Nd3+:YVO4 microchip laser with wavelength of 1064 nm is employed as a modulation source to modulate the population of both ground and excited state of Cr4+:YAG simultaneously. A polarized beam-splitter(PBS) is used to direct the modulation beam onto the Cr4+:YAG crystal. A focus lens in front of the microchip laser is used for shaping the laser beam to match with the cavity mode. A function generator is used to provide the microchip laser a modulated pumping source. The timing jitter modulated with the microchip laser is then monitored by a 500 MHz digital scope. The experimental result has shown that the external modulation by a microchip laser proposed by us indeed improve the timing jitter up to 50%.
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Chen, Chien-Hwo y 陳建豪. "Period-Doubling Route to Chaos in a Passive Q-Switched Nd：YAG Laser with a Cr4+：YAG Saturable Absorber". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/43719068783351786735.
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碩士逢甲大學
光電物理研究所
92
We study the nonlinear dynamic behavior in a passive Q-switched Nd:YAG laser system with a Cr4+:YAG saturable absorber. By operating in transverse-mode-degeneracy cavity, we find the doubling-route to chaos near the threshold. We find that the bifurcation accompanies with the low order of the transverse mode by analyzing the mode pattern variation. Therefore, we can confirm our mechanism should belong to multi-transverse mode competition, and the mechanism is different from the previous study. Besides, we also find the period-doubling route to chaos beginning from period 3、period 5 and period 7. By calculating correlation dimensions of the chaotic signals for the tradition route and the one beginning from period 3, the dimensions are 4.583 0.044 and 4.456 0.059, respectively. Thus, we think that the latter one is the periodic windows in a period-doubling route to chaos.
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He, Sheng-Ting y 何昇庭. "Exploring Tail Removal of Passive Q-switched Pulse Nd:YAG Laser by Using Diffraction Intra-cavity Round Trip Loss". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/82621108341429678324.
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碩士國立交通大學
理學院應用科技學程
105
The technique of pulsed pumping millijoule laser is well-developed in ophthalmology field and the related application. In this thesis, we utilize flash-pumped source to excite the Nd:YAG crystal and insert Cr4+:YAG to be the satuable absorber as forming the Q-switched operation. The cavity is set by a plano-convex mirror and concave-convex mirror, which is an unstable cavity with 90-mm-long cavity length. We measure the total output energy, laser-induced air breakdown threshold energy and laser output signal in time domain by exploiting different combinations of the radius of curvature of front mirrors and output couplers. We demonstrate the experimental results and explain the relationship between the cavity mirrors and the threshold energy through the output pulse shape in temporal domain
46
Hong, Yi-Rui y 洪一瑞. "A study on the general performance of a diode-pumped passively Q-Switched Nd:YVO4 laser". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/62859536964063790031.
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碩士淡江大學
物理學系
91
The output of a of diode-pumped passively Q-switched lasers is closely related to the pumping condition; however, this type of lasers are usually treated in theory by rate- equation models in which the effects of pump light on laser are neglected; the relationship between the laser output and pumping condition is thus ignored. In this thesis we investigate the output characteristics of Nd:YVO4/Cr4+:YAG Q-switched lasers using rate equations allowing for the effects of pump and the decay of relevant energy levels.Experiments on CW Nd:YVO4 lasers and second threshold of YVO4/Cr4+:YAG lasers were performed prior to our theoretical calculations so that laser parameters (the effective stimulated emission cross section of the gain medium, s, and the absorption cross section of Cr4+:YAG, ss) can be determined, and the simulation done with our rate-equation model can be justified for the CW cases.It is noted that the Q-switched laser experiment on the second threshold not only allow us to determine the value of ss but also clearly shows how the transition between CW- and Q-switched modes of operations occurs.Finally, simulations of Nd:YVO4/Cr4+:YAG Q-switched lasers were performed with the experimentally determined cross sections. It turns out that our theoretical model can predict the general performance of the laser very well qualitatively, and the calculated results are also close to our experimental findings.
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Huang, Chin-Hao y 黃金豪. "Master Oscillator of Fiber Power Amplifier Seeded by Nd:YVO4/Cr4+:YAG Passively Q-Switched Laser". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23406166527188827346.
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碩士國立交通大學
理學院應用科技學程
99
We report on an analysis of the design guideline of a hemispherical resonator Nd:YVO4/Cr4+:YAG passively Q-Switched (PQS) laser by optimization of the mode matching condition and agreement with the good PQS criterion. Cr4+:YAG saturable absorbers with various initial transmission were used to investigate the performances of the laser configuration. Then we inject these high-peak-power PQS laser to realize the single-stage, linear-polarized fiber amplifier. With the seed laser of pulse repetition rate (PRR) of 50 kHz, the amplifier emits pulse energy of 178 and peak power of 37 kW under the pump power of 16 W. With the seed laser of PRR of 25 kHz, we can attain the amplifier with pulse energy of 192 and peak power of 113 kW under the pump power of 10 W which is restricted by the fiber facet damage.
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Chen, Yu-Chen y 陳昱辰. "Design and application of quasi-CW diode-side-pumped milli-joule passively Q-switched laser". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/21451164844629163586.
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碩士國立交通大學
電子物理系所
102
High-peak-power eye-safe pulsed lasers have been widely used in industry applications. In this thesis, we utilize the Nd:YVO4 and the Nd:YLF crystals as gain mediums with the Cr4+:YAG crystal as the saturable absorber to explore a passively Q-switched laser. Through the theoretical analysis of second threshold condition, we adopt the design of nearly hemispherical cavity and the diode-side-pumping configuration to realize the high peak power output. Futhermore, we demonstrate the eye-safe laser by adding the KTP crystal to perform the extracavity optical parametric oscillation for converting the lasing wavelength from 1 um to 1.5 um. In the experiment of Nd:YVO4 PQS laser, the output pulse energy reaches 3 mJ and the peak power is 100 kW. For the OPO operation, we obtain a 1.4-mJ output pulse energy with the peak power of 100 kW. On the other hand, the output pulse energy of 20 mJ with the peak power up to 950 kW can be attained by utilizing the Nd:YLF crystal as the gain medium. We further realize the eye-safe laser with pulse energy of 10 mJ and peak power of 600 kW through the OPO operation.
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Shin-HaoHung y 洪士豪. "Passively Q-switched erbium all-fiber lasers by use of thulium doped saturable-absorber fibers". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/90636310769732091982.
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碩士國立成功大學
微電子工程研究所碩博士班
98
We demonstrate all-fiber passively Q-switched erbium lasers at 1570 nm using Tm3+-doped saturable-absorber fibers. The absorption cross section of a Tm3+-doped fiber at 1570 nm was measured in a bleaching experiment to be about 1.44?10-20 cm2. With a thulium-doped fiber, sequential pulses with a pulse energy of 9??J and a pulse duration of about 420 ns were stably produced at repetition rates in the range 0.1 to 3 kHz. The corresponding deviation of the repetition-rate stability was 4 to 188Hz. The loss caused by photo-darkening was about 12% after a long time operation. The maximum pulse repetition rate was 6 kHz, limited by the maximum pump power of a 980- nm laser diode, about 230 mW.
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Chang, Yu Chang y 張裕昌. "Energy adjustable passively Q-switched micro-laser with a diffusion-bonded Nd:YAG/Cr4+:YAG crystal". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/8mxx99.
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碩士國立交通大學
理學院應用科技學程
103
To demonstrate an energy adjustable passively Q-switched laser, a diode laser pumped Nd:YAG crystal diffusion-boned with a wedged Cr4+:YAG crystal is utilized. By changing the transverse pump location of the laser diode on the laser crystal, the initial transmission of the saturable absorber can be flexibly adjusted to achieve the variation of output pulse energy. The experimental result for different crystal length and different pump area are also shown in the thesis. In addition, the multi-transverse-mode output is eliminated to maintain good beam quality by controlling the input power and pump location. For further applications, the 1064-nm PQS laser is utilized to generate a frequency-double 532-nm laser. Finally, the whole set of the green laser is modular in order to be used in actual industrial demand.