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1
Ablikim, Utuq. "Fragmentation of molecular ions in ultrafast laser pulses." Kansas State University, 2015. http://hdl.handle.net/2097/18962.
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Master of ScienceDepartment of Physics
Itzhak Ben-Itzhak
Imaging the interaction of molecular ion beams with ultrafast intense laser fields is a very powerful method to understand the fragmentation dynamics of molecules. Femtosecond laser pulses with different wavelengths and intensities are applied to dissociate and ionize molecular ions, and each resulting fragmentation channel can be studied separately by implementing a coincidence three-dimensional (3D) momentum imaging method. The work presented in this master’s report can be separated into two parts. First, the interaction between molecular ion beams and femtosecond laser pulses, in particular, the dissociation of CO[superscript]+ into C[superscript]++O, is studied. For that purpose, measurements are conducted at different laser intensities and wavelengths to investigate the possible pathways of dissociation into C[superscript]++O. The study reveals that CO[superscript]+ starts to dissociate from the quartet electronic state at low laser intensities. Higher laser intensity measurements, in which a larger number of photons can be absorbed by the molecule, show that the doublet electronic states with deeper potential wells, e.g. A [superscript]2Π, contribute to the dissociation of the molecule. In addition, the three-body fragmentation of CO[subscript]2[superscript]+ into C[superscript]++O[superscript]++O[superscript]+ is studied, and two breakup scenarios are separated using the angle between the sum and difference of the momentum vectors of two O[superscript]+ fragments. In the second part, improvements in experimental techniques are discussed. Development of a reflective telescope setup intended to increase the conversion efficiency of ultraviolet (UV) laser pulse generation is described, and the setup is used in the studies of CO[superscript]+ dissociation described in this report. The other technical study presented here is the measurement of the position dependence of timing signals picked off of a microchannel plate (MCP) surface. The experimental method is presented and significant time spread over the surface of the MCP detector is reported [1].
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Akturk, Selcuk. "Extending ultrashort-laser-pulse measurement techniques to new dimensions, time scales, and frequencies." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6892.
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In the last decade, there has been tremendous progress in the field of ultrashort-pulse measurement. However, this effort has focused mostly on the temporal behavior of 100-fs, 800-nm ultrashort pulse, ignoring other pulse lengths, wavelengths, and the very common space-time couplings or so called spatio-temporal distortions. In this thesis work, I do an extensive study of spatio-temporal distortions and their measurement using Frequency Resolved Optical Gating (FROG) and its relatives. I clarify some ambiguities in the descriptions of these effects in the existing theory and establish a more general description of such distortions in ultrashort pulses. I also extend these measurement techniques to different wavelengths and pulse lengths. Specifically, I develop measurement devices for few-cycle NIR pulses, weak and narrowband fiber laser pulses, long (several-ps) NIR pulses, and visible pulses from NOPAs.
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Papastathopoulos, Evangelos. "Adaptive control of electronic excitation utilizing ultrafast laser pulses." Doctoral thesis, [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975015184.
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Lee, Dongjoo. "Ultra-broadband phase-matching ultrashort-laser-pulse measurement techniques." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07032007-113912/.
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Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2008.First, Phillip, Committee Member ; Adibi, Ali, Committee Member ; Raman, Chandra, Committee Member ; Buck, John, Committee Member ; Trebino, Rick, Committee Chair.
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Macpherson, James. "Characterisation and Optimization of Ultrashort Laser Pulses." Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/1237.
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The ultrafast optical regime is defined, as it applies to laser pulses, along with a brief introduction to pulse generation and characterisation technologies. A more extensive description of our particular amplified pulse generation and SPIDER characterisation systems follows. Data verifying the correct operation of the characterisation system is presented and interpreted. Our laser system is then characterised in two different configurations. In each case, the data describing the system is presented and analyzed. Conclusions are made regarding the performance of both the characterisation and laser systems, along with suggested improvements for each.
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Al-Jarah, Uday Ali Sabeeh. "Modification and monitoring of magnetic properties with ultrafast laser pulses." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/9252.
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Investigations of the static and dynamic electronic, optical and acoustic properties of different nanostructures are presented. Magneto-optical Kerr effect (MOKE) magnetometry has been used to probe the magnetic properties of the magnetic nanostructures. A time-resolved all-optical pump-probe technique, using femtosecond laser pulses, has been employed to investigate the ultrafast magnetisation dynamics, and transient polarisation and reflectivity responses. The magnetic samples studied were permalloy (NiFe) nanowire arrays and multilayered CoNi/Pt films and nanodot arrays, while the non-magnetic samples were phase change GeSbTe thin films. These structures have attracted much attention because their properties can be advantageous in data storage applications. Static MOKE measurements of the NiFe nanowires revealed zero coercivity and remanence, regardless of the direction of the applied magnetic field, with the magnetic easy axis perpendicular to the axis of the nanowire. This is the result of antiferromagnetic alignment of the magnetization in adjacent nanowires at remanence. Time-resolved MOKE (TRMOKE) measurements performed upon the nanowires showed increasing demagnetisation with increasing pump fluence, with a larger response being observed when the magnetic field was applied perpendicular to the nanowire axis. This behaviour, together is believed to result from the formation of vortices at the end of the nanowires. Moreover, the TRMOKE response revealed oscillations due to modes of magnetic precession with frequencies that have minima at a field rather close to the saturation field of the samples. For lower fields, the frequencies decrease with increasing applied field, while for higher fields, they increase with increasing applied field. This behaviour is believed to result from the strong dipolar interactions that can overwhelm the shape anisotropy of an individual nanowire leading to a switching of the easy axis from parallel to perpendicular to the nanowire axis. The magnetisation may also break up into domains for field values less than the saturation value, which results in a decrease in the dipolar coupling with decreasing applied field. Static MOKE measurements of the CoNi/Pt multilayers showed that the saturation Kerr rotation increases with increasing packing density of the sample, while the coercive field decreases after patterning, but increases with decreasing diameter among the patterned samples. AC-MOKE measurements revealed that increasing pump fluence leads to decreasing coercivity and increasing demagnetisation, which is attributed to the increased heating of the surface of the dots and, thus, an increased temperature. Full demagnetisation and total loss of coercivity were achieved for all the nanodot arrays. The AC-MOKE results are in good agreement with the results of TRMOKE measurements. Transient polarisation measurements showed a clear specular-optical Kerr effect (SOKE) response for all the samples. This response appears as a peak at the zero delay position that has maximum (zero) effect when the pump and probe electric fields lie 450 (00 or 900) apart, and is accompanied by longer-lived damped oscillatory modes for the nanowires and nanodot arrays. A mechanism involving the optically induced electric polarisation of the nanodots and nanowires has been suggested to explain this response. Moreover, an epitaxial GeSbTe film revealed a robust dependence of the transient polarisation upon the sample orientation which suggests a strong influence of the crystallographic structure for this sample. The time-resolved reflectivity (TRR) measurements for the nanowire and nanodot arrays revealed a linear dependence of the amplitude of the transient reflectivity upon the pump fluence. A number of oscillatory modes with different GHz frequencies were observed to be superimposed upon an exponentially relaxing background, while a single mode was observed in the CoNi/Pt continuous film. These oscillations are believed to result from the excitation of surface acoustic waves (SAW). Two principal mechanisms have been suggested to explain the excitation of SAWs within the nanodot arrays. A discrepancy between the experimental and frequencies predicted by an existing model was found which is believed to be due to the neglect of the sample composition and the SAW velocity of the nanostructures within this model. The development of a model that overcomes these weaknesses is suggested for future work. An additional THz frequency mode was observed within the GeSbTe which is believed to arise from the excitation of optical and acoustic phonon modes. Further work is required to identify the observed phonon modes and to relate the associated optically induced linear birefringence to a specific structural distortion.
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Manescu, Corneliu. "Controlling and probing atoms and molecules with ultrafast laser pulses." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004411.
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Wong, Tsz Chun. "Single-shot measurements of complex pulses using frequency-resolved optical gating." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50335.
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Frequency-resolved optical gating (FROG) is the standard for measuring femtosecond laser pulses. It measures relatively simple pulses on a single-shot and complex pulses using multi-shot scanning and averaging. However, experience from intensity autocorrelation suggests that multi-shot measurements may suffer from a coherent artifact caused by instability in the laser source. In this thesis, the coherent artifacts present in modern pulse measurement techniques are examined and single-shot techniques for measuring complex pulse(s) are proposed and demonstrated. The study of the coherent artifact in this work shows that modern pulse measurement techniques also suffer from coherent artifacts and therefore single-shot measurements should be performed when possible. Here, two single-shot experimental setups are developed for different scenarios. First, an extension of FROG is developed to measure two unknown pulses simultaneously on a single-shot. This setup can measure pulses that have very different center wavelengths, spectral bandwidths, and complexities. Second, pulse-front tilt is incorporated to extend the temporal range of single-shot FROG to tens of picoseconds which traditionally can only be attained by multi-shot scanning. Finally, the pulse-front tilt setup is modified to perform a single-shot measurement of supercontinuum, one of the most difficult pulses to measure due to its long temporal range, broad spectral bandwidth, and low pulse energy.
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Cortelli, Giorgio. "Ultrafast electron diffraction on materials exposed to intense free electron laser pulses." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19305/.
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The advent of Free Electron Lasers (FELs) has opened unprecedented opportunities for the study of transient states of matter. The use of the seeding technique, developed at the FERMI FEL in Trieste (Italy), pushed further the frontier allowing to perform pump-probe experiments with femtosecond time resolution. FELs permit shedding light onto unexplored non-equilibrium dynamics and processes in matter. In this thesis, a pioneering setup for monitoring sub-picosecond atomic structure changes in materials is described. The FEL is used as an isochoric pump while a 100 keV compressed electron bunch is used as a structural probe thus obtaining an ultrafast electron diffraction (UED) facility. Results of a pilot UED experiment on selected samples (gold and diamond) are presented and analysed.
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Barbieri, Nicholas. "Engineering and Application of Ultrafast Laser Pulses and Filamentation in Air." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5602.
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Continuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter. The need to better control the light obtained from increasingly advanced laser sources leads to the emergence of beam engineering, the systematic understanding and control of light through refractive media and free space. Beam engineering enables control over the beam shape, energy and spectral composition during propagation, which can be achieved through a variety of means. In this dissertation, several methods of beam engineering are investigated. These methods enable improved control over the shape and propagation of laser light. Laser-matter interaction is also investigated, as it provides both a means to control the propagation of pulsed laser light through the atmosphere, and provides a means to generation remote sources of radiation.Ph.D.
Doctorate
Physics
Sciences
Physics
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Harper, Matthew R. "Control and measurement of ultrafast pulses for pump/probe-based metrology." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/430.
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Chatelain, Robert P. 1982. "RF compression of electron bunches applied to ultrafast electron diffraction." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111943.
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The dynamics of atomic scale structures during structural change can be studied by Ultrafast Electron Diffraction (UED). The time resolution needed to reveal the fastest dynamics is 100 fs. Sub-angstrom structural resolution becomes possible with 1-1000 pC of charge necessary for diffraction pattern analysis during subtle structural changes. This combination of requirements cannot currently be realized due to the space-charge temporal broadening inherent to bunches of electrons of high fluence and short temporal duration. Simulations show that the incorporation of a specially designed Radio-Frequncy (RF) cavity into the UED apparatus removes this technical limitation. The RF cavity reverses the near linear position-momentum distribution of the temporally broadened electron bunch, causing the bunch to recompress itself as it propagates. It is found that our proposed method allows for sub-100 fs bunches with maximum charge of 0.6 pC, almost 3 orders of magnitude improvement over today's state of the art.
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Mang, Matthias M. "Interferometric spatio-temporal characterisation of ultrashort light pulses." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:163c5374-1466-4c4d-a0f5-c4e66b27e2ac.
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The main topic of this thesis is the development of novel diagnostics for the characterisation of infrared femtosecond and extreme-ultraviolet (XUV) attosecond pulses. High-resolution interferometric methods are applied to high harmonic radiation, both to measure the properties of the XUV light and to relate this information to the physics of the fundamental generation process. To do so, a complete high harmonic beamline has been built and optimised to enable the observation of strong signatures of the macroscopic response of the medium. The distinct spatial characteristics of long and short trajectories are studied, as well as the interference between them. An interferometric measurement allows the extraction of the atomic dipole phase, which gives direct access to the sub-cycle electron dynamics. A major focus of this thesis is on the development of a novel method which simultaneously characterises two independent electric fields as a function of any degree of freedom in which it is possible to shear one of the beams. Since each field alternately takes the role of the reference to retrieve the other field, this technique is referred to as mutual interferometric characterisation of electric-fields (MICE). One of the key features of MICE is that no sheared but otherwise identical replica of the test pulse needs to be generated, which is a typical requirement of self-referencing techniques. Furthermore, no a priori information is needed for the reconstruction. The strength and the wide applicability of MICE are demonstrated using two fundamentally different examples. First, the temporal pulse profiles of two infrared femtosecond pulses are simultaneously reconstructed in a single laser shot. In the second demonstration, the MICE approach is used to simultaneously reconstruct the wavefronts of two high harmonic beams. Having this new technique at hand, the phase properties of the different quantum trajectories are compared. All pulse characterisation techniques implicitly assume full coherence of the beam. This, however, is often not the case in practice, in particular when dealing with complex XUV light sources. Here the standard characterisation techniques fail to provide an accurate description of the electric field. Instead, the electric field must be seen as a statistical mixture of different contributions to the overall field. Here an interferometric experiment is first proposed and then performed involving multiple lateral shears to measure the two-point correlation function of high harmonic radiation. This directly provides information about the existence and the magnitude of partial coherence of high harmonics.
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Popa, Daniel. "Ultrafast fiber lasers mode-locked by carbon nanotubes and graphene." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648103.
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Graham, Leigh. "Quantum control of laser induced dynamics of diatomic molecular ions using shaped intense ultrafast laser pulses." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602512.
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The beauty of ultrafast science lies inherently in the ability to induce and image dynamics on a timescale comparable to the fastest nuclear motion, In recent years, a plethora of rich and fascinating phenomena involving the interaction of diatomic molecules with intense femtosecond laser pulse has been unveiled, Such research is motivated by the ambition to understand and optically drive chemical reactions to the highest degree of specificity, In this work, the strategy employed toward achieving this goal relies ., on the interaction of Hydrogenic ions and analytically shaped and well characterized pulses, The ability to manipulate photodissociation dynamics using the instantaneous frequency and temporal profile of pulses shaped with quadratic (ψ") and cubic (ψ’") spectral phase functions was studied, A three-dimensional (3D) momentum imaging technique was used to measure the kinetic energy release (KER) and angular distribution of the dissociation fragments, A significant enhancement in the dissociation probability of non-resonant transitions from the low lying vibrational levels using the sign and magnitude of the applied phase function as a control tool was demonstrated, Furthermore, the tractability of Hydrogenic ions means a mechanistic explanation for these observations can be theoretically determined, Investigating the behavior of ions more complex than H+2 in strong laser fields can present many theoretical and experimental challenges, Laser-induced fragmentation of CD+ was explored using the 3D momentum imaging technique in the longitudinal field imaging mode, The high mass ratio (12:2) hinders the simultaneous measurement of the two constituents, at all angles and kinetic energies, Alternatively, the recently developed longitudinal and transverse field imaging technique was used to perform a piecewise dissociation measurement, This allowed the branching ratio of the dissociation channels to be obtained, Furthermore, the fragmentation channels of CD+ were identified and studied as a function of laser intensity and wavelength,
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Balasubramanian, Haribhaskar. "Two photon luminescence from quantum dots using broad and narrowband ultrafast laser pulses." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2020.
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Labeye, Marie. "Molecules interacting with short and intense laser pulses : simulations of correlated ultrafast dynamics." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS193/document.
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Cette thèse porte sur différents aspects des dynamiques ultra-rapides d’atomes et de molécules soumises à des impulsions laser infrarouges courtes et intenses. Nous étudions des processus fortement non linéaires tels que l’ionisation tunnel, la génération d’harmoniques d’ordre élevé ou l’ionisation au-dessus du seuil. Deux approches différentes sont utilisées. D’un côté nous mettons au point des modèles analytiques approchés qui nous permettent de construire des interprétations physiques de ces processus. D’autre part nous appuyons les interprétations données par ces modèles avec les résultats obtenus par des simulations numériques qui résolvent explicitement l’équation de Schrödinger dépendante du temps en dimension réduite. Nous étudions également une méthode numérique basée sur l’interaction de configuration dépendante du temps afin de pouvoir des décrire des systèmes à plusieurs électrons plus gros et plus complexesIn this thesis we study different aspects of the ultrafast dynamics of atoms and molecules triggered by intense and short infrared laser pulses. Highly non-linear processes like tunnel ionization, high order harmonic generation and above threshold ionization are investigated. Two different and complementary approaches are used. On the one hand we construct approximate analytical models to get physical insight on these processes. On the other hand, these models are supported by the results of accurate numerical simulations that explicitly solve the time dependent Schrödinger equation for simple benchmark models in reduced dimensions. A numerical method based on time dependent configuration interaction is investigated to describe larger and more more complex systems with several electrons
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Inoue, Shunsuke. "Femtosecond Electron Deflectometry for Measuring Ultrafast Transient Fields Induced by Intense Laser Pulses." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175109.
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Chiasson, Martin. "An Imaging Mass Spectrometer with Ultrashort Laser Pulses as its Ionization Source." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34343.
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We have built an imaging mass spectrometer adapted for ultrashort laser pulses as its ionization technique, as an alternative to other imaging techniques. Before my arrival, the mass spectrometer has only been subject to preliminary tests on noble gases. Since then, we’ve made some modifications to the system in order to properly analyze solids. This thesis shows how we obtain our ultrashort laser pulses, the inner workings of our homemade imaging mass spectrometer, and the results that we’ve obtained with it so far. We tested two modes of operation concerning the extraction of the ions from the system into the mass analyzer: continuous and pulsed. We discuss the advantages and disadvantages of each configuration. We also display preliminary imaging results with our imaging technique of a simple WO3 and ITO structure. We conclude by comparing the resolution of this image to the different techniques in imaging mass spectrometry, how we can further improve our mass spectrometer, and the future use of this machine.
Nous avons construit un spectromètre de masse adapté pour les pulses de laser très courts comme technique d’ionisation, pour acquisition des images d’un échantillon. Avant je suis arrivé, le spectromètre de masse avait seulement été utilisé pour des tests préliminaires de gaz nobles. Depuis ce moment, nous avons modifié le système pour analyser les solides. Cette thèse démontre comment on obtient nos pulses de laser très courts, comment notre spectromètre fait maison fonctionne et les résultats nous avons obtenus jusqu’à présent. Nous avons testé deux configurations différentes au sujet de l’extraction des ions du système : constant et pulsé. Nous discutons aussi les avantages et désavantages de chaque mode d’opération. Nous démontrons aussi des images préliminaires d’un substrat mixte de WO3 et ITO. Nous concluons par comparer la résolution des images aux autres techniques de collection d’images, comment nous pouvons améliorer notre spectromètre de masse et les plans pour la machine dans le futur.
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Morrison, Vance. "Generation of tunable femtosecond laser pulses and the construction of an ultrafast pump-probe spectrometer." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116114.
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An ultrafast UV-visible spectrometer was designed and implemented. An optical parametric amplifier was constructed to be used as a pump source for the spectrometer. Using nonlinear optical processes and an 800 nm ultrashort pulses, tunable infrared(IR) light was produced with a wavelength range of ∼.1 mum to 3 mum. The IR light was then mixed with 800 nm light to produce tunable visible light with a wavelength range of 466 nm to 600 nm. Supercontinuum (SC) was used as the probe pulse of the spectrometer, providing a large observation bandwidth. Commercially purchased fast spectrometers were used as the detection mechanism. The characterization of the set up, as well the observation of some ultrafast molecular dynamics observed in 8-hydroxy-1,3,6-pyrenetrisulfonic acid, are presented.
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McAlister, Daniel Frank. "Measuring the classical and quantum states and ultrafast correlations of optical fields /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9948024.
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Thesis (Ph. D.)--University of Oregon, 1999.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 197-201). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948024.
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Jakob, Markus Alexander [Verfasser]. "Generation and Control of Ultrafast 10 um Laser Pulses for Driving Chemical Dynamics / Markus Alexander Jakob." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219475904/34.
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Chini, Michael. "Characterization and Application of Isolated Attosecond Pulses." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5163.
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Tracking and controlling the dynamic evolution of matter under the influence of external fields is among the most fundamental goals of physics. In the microcosm, the motion of electrons follows the laws of quantum mechanics and evolves on the timescale set by the atomic unit of time, 24 attoseconds. While only a few time-dependent quantum mechanical systems can be solved theoretically, recent advances in the generation, characterization, and application of isolated attosecond pulses and few-cycle femtosecond lasers have given experimentalists the necessary tools for dynamic measurements on these systems. However, pioneering studies in attosecond science have so far been limited to the measurement of free electron dynamics, which can in most cases be described approximately using classical mechanics. Novel tools and techniques for studying bound states of matter are therefore desired to test the available theoretical models and to enrich our understanding of the quantum world on as-yet unprecedented timescales. In this work, attosecond transient absorption spectroscopy with ultrabroadband attosecond pulses is presented as a technique for direct measurement of electron dynamics in quantum systems, demonstrating for the first time that the attosecond transient absorption technique allows for state-resolved and simultaneous measurement of bound and continuum state dynamics. The helium atom is the primary target of the presented studies, owing to its accessibility to theoretical modeling with both ab initio simulations and to model systems with reduced dimensionality. In these studies, ultrafast dynamics - on timescales shorter than the laser cycle - are observed in prototypical quantum mechanical processes such as the AC Stark and ponderomotive energy level shifts, Rabi oscillations and electromagnetically-induced absorption and transparency, and two-color multi-photon absorption to "dark" states of the atom. These features are observed in both bound states and quasi-bound autoionizing states of the atom. Furthermore, dynamic interference oscillations, corresponding to quantum path interferences involving bound and free electronic states of the atom, are observed for the first time in an optical measurement. These first experiments demonstrate the applicability of attosecond transient absorption spectroscopy with ultrabroadband attosecond pulses to the study and control of electron dynamics in quantum mechanical systems with high fidelity and state selectivity. The technique is therefore ideally suited for the study of charge transfer and collective electron motion in more complex systems. The transient absorption studies on atomic bound states require ultrabroadband attosecond pulses ? attosecond pulses with large spectral bandwidth compared to their central frequency. This is due to the fact that the bound states in which we are interested lie only 15-25 eV above the ground state, so the central frequency of the pulse should lie in this range. On the other hand, the bandwidth needed to generate an isolated 100 as pulse exceeds 18 eV - comparable to or even larger than the central frequency. However, current methods for characterizing attosecond pulses require that the attosecond pulse spectrum bandwidth is small compared to its central frequency, known as the central momentum approximation. We therefore explore the limits of attosecond pulse characterization using the current technology and propose a novel method for characterizing ultrabroadband attosecond pules, which we term PROOF (phase retrieval by omega oscillation filtering). We demonstrate the PROOF technique with both simulated and experimental data, culminating in the characterization of a world-record-breaking 67 as pulse.Ph.D.
Doctorate
Physics
Sciences
Physics
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Kim, Ki-Yong. "Measurement of ultrafast dynamics in the interaction of intense laser pulses with gases, atomic clusters, and plasmas." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/93.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2003.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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Vaughan, Peter Matthias. "Optical-parametric-amplification applications to complex images." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41134.
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We have used ultrafast optics, primarily focused on the nonlinear processes of Polarization Gating and of Optical Parametric Amplification, one for measurement and the other for imaging purposes. For measurement, we have demonstrated a robust method of measurement to simultaneously measure both optical pulses used in a pump-probe type configuration. We refer to this method of pulse measurement as Double Blind Polarization Gating FROG. We have demonstrated this single-shot method for measuring two unknown pulses using one device. In addition to pulse measurement, we have demonstrated the processes of Optical Parametric Amplification (OPA) applicability to imaging of complex objects. We have done this where the Fourier transform plane is used during the interaction. We have amplified and wavelength converted a complex image. We observe a gain of ~100, and, although our images were averaged over many shots, we used a single-shot geometry, capable of true single-shot OPA imaging. To our knowledge, this is the first Fourier-plane OPA imaging of more than a single spatial-frequency component of an image. We observe more than 30 distinct spatial frequency components in both our amplified image and our wavelength shifted image. We have demonstrated all-optical spatial filtering for these complex images. We have demonstrated that direct Fourier filtering of spatial features is possible by using a shaped pump beam. We can isolate certain portions of the image simply by rotating the crystal.
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Talisa, Noah Brodzik. "Laser-Induced Damage and Ablation of Dielectrics with Few-Cycle Laser Pulses." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1609243476481238.
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Bubelnik, Matthew. "THE EFFECTS OF ELECTRODE GEOMETRY ON CURRENT PULSE CAUSED BY ELECTRICAL DISCHARGE OVER AN ULTRA-FAST LASER FILAMENT." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3695.
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The time-resolved electrical conductivity of a short-pulse generated plasma filament in air was studied. Close-coupled metal electrodes were used to discharge the stored energy of a high-voltage capacitor and the resulting microsecond-scale electrical discharge was measured using fast current sensors. Significant differences in the time dependence of the current were seen with the two electrode geometries used. Using sharp-tipped electrodes additional peaks in the time-resolved conductivity were seen, relative to the single peak seen with spherical electrodes. We attribute these additional features to secondary electron collisional ionization brought about by field enhancement at the tips. Additional discrepancies in the currents measured leaving the high-voltage electrode and that returning to ground were also observed. Implications for potential laser-induced discharge applications will be discussed.M.S.
Other
Optics and Photonics
Optics
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Austin, Dane R. "High-resolution interferometric diagnostics for ultrashort pulses." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:03ff32ea-c82a-4a42-9c6b-11e42ddb1e67.
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I present several new methods for the characterisation of ultrashort pulses using interferometry. A generalisation of the concatenation algorithm for spectral shearing interferometry enables interferograms taken at multiple shears to be combined. This improves the precision of the reconstructed phase in the presence of detector noise, and enables the relative phase between disjoint spectral components to be obtained without decreasing the spectral resolution. The algorithm is applied to experimental data from two different implementations of spectral shearing interferometry for ultrashort optical pulses. In one, the shears are acquired sequentially, and in the other they are acquired simultaneously. I develop a form of spatio-temporal ultrashort pulse characterisation which performs both spatial and spectral shearing interferometry simultaneously. It requires a similar geometrical setup to common implementations of spectral phase interferometry for direct electric-field reconstruction, but provides complete amplitude and phase characterisation in time and one spatial dimension. I develop the theory of lateral shearing interferometry for spectrally resolved wavefront sensing of extended ultraviolet and soft x-ray pulses generated using high-harmonic generation. A comprehensive set of wavefront measurements of harmonics 13-25 in Krypton show good agreement with theory, validating the technique. I propose and numerically demonstrate quantum-path interferometry mediated by a weak control field for high harmonic generation. This is a general technique for measuring the amplitude and relative phases of each contributing quantum path. The control field perturbatively modulates the phase of each path. The differing sensitivity of each path to the parameters of the control field allows their contributions to be distinguished from one another.
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Jönsson, Olof. "Ultrafast Structural and Electron Dynamics in Soft Matter Exposed to Intense X-ray Pulses." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331936.
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Investigations of soft matter using ultrashort high intensity pulses have been made possible through the advent of X-ray free-electrons lasers. The last decade has seen the development of a new type of protein crystallography where femtosecond dynamics can be studied, and single particle imaging with atomic resolution is on the horizon. The pulses are so intense that any sample quickly turns into a plasma. This thesis studies the ultrafast transition from soft matter to warm dense matter, and the implications for structural determination of proteins. We use non-thermal plasma simulations to predict ultrafast structural and electron dynamics. Changes in atomic form factors due to the electronic state, and displacement as a function of temperature, are used to predict Bragg signal intensity in protein nanocrystals. The damage processes started by the pulse will gate the diffracted signal within the pulse duration, suggesting that long pulses are useful to study protein structure. This illustrates diffraction-before-destruction in crystallography. The effect from a varying temporal photon distribution within a pulse is also investigated. A well-defined initial front determines the quality of the diffracted signal. At lower intensities, the temporal shape of the X-ray pulse will affect the overall signal strength; at high intensities the signal level will be strongly dependent on the resolution. Water is routinely used to deliver biological samples into the X-ray beam. Structural dynamics in water exposed to intense X-rays were investigated with simulations and experiments. Using pulses of different duration, we found that non-thermal heating will affect the water structure on a time scale longer than 25 fs but shorter than 75 fs. Modeling suggests that a loss of long-range coordination of the solvation shells accounts for the observed decrease in scattering signal. The feasibility of using X-ray emission from plasma as an indicator for hits in serial diffraction experiments is studied. Specific line emission from sulfur at high X-ray energies is suitable for distinguishing spectral features from proteins, compared to emission from delivery liquids. We find that plasma emission continues long after the femtosecond pulse has ended, suggesting that spectrum-during-destruction could reveal information complementary to diffraction.
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Moreno, Ivan Daniel. "Towards the Investigation of Ultrafast Directed Excite-State Isomerization in BBR3 and PBR3 with sub-50 fs Deep-UV/UV laser pulses." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1404740168.
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Vaupel, Andreas. "High Energy, High Average Power, Picosecond Laser Systems to Drive Few-Cycle OPCPA." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5881.
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The invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA allows direct amplification of an almost-octave spanning bandwidth supporting few-cycle pulse durations at center wavelengths ranging from the visible to the mid-IR. The current record in peak power from a table-top OPCPA is 16 TW and the current record average power is 22 W. High energy, few-cycle pulses with stabilized carrier-envelope phase (CEP) are desired for applications such as high-harmonic generation (HHG) enabling attoscience and the generation keV-photon bursts. This dissertation conceptually, numerically and experimentally describes essential aspects of few-cycle OPCPA, and the associated pump beam generation. The main part of the conducted research was directed towards the few-cycle OPCPA facility developed in the Laser Plasma Laboratory at CREOL (University of Central Florida, USA) termed HERACLES. This facility was designed to generate few-cycle pulses in the visible with mJ-level pulse energy, W-level average power and more than 100 GW peak power. Major parts of the implementation of the HERACLES facility are presented. The pump generation beam of the HERACLES system has been improved in terms of pulse energy, average power and stability over the last years. It is based on diode-pumped, solid-state amplifiers with picosecond duration and experimental investigations are presented in detail. A robust system has been implemented producing mJ-level pulse energies with ~100 ps pulse duration at kHz repetition rates. Scaling of this system to high power (>30 W) and high peak power (50-MW-level) as well as ultra-high pulse energy (>160 mJ) is presented. The latter investigation resulted in the design of an ultra-high energy system for OPCPA pumping. Following this, a new OPCPA facility was designed termed PhaSTHEUS, which is anticipated to reach ultra-high intensities. Another research effort was conducted at CELIA (Univerist&"233; de Bordeaux 1, France) and aimed towards a previously unexplored operational regime of OPCPA with ultra-high repetition rates (10 MHz) and high average power. A supercontinuum seed beam generation has been established with an output ranging from 1.3 to 1.9 ?m and few ps duration. The pump beam generation has been implemented based on rod-type fiber amplifiers producing more than 37 W average power and 370 kW peak power. The utility of this system as an OPCPA pump laser is presented along with the OPA design. The discussed systems operate in radically different regimes in terms of peak power, average power, and repetition rate. The anticipated OPCPA systems with few-cycle duration enable a wide range of novel experimental studies in attoscience, ultrafast materials processing, filamentation, LIBS and coherent control.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Schorb, Sebastian [Verfasser], and Thomas [Akademischer Betreuer] Möller. "Size-dependent ultrafast ionization dynamics of nanoscale samples in intense femtosecond x-ray free-electron laser pulses / Sebastian Schorb. Betreuer: Thomas Möller." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1027798306/34.
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Jacqmin, Hermance. "Coherent combining of few-cycle pulses for the next generation of Terawatt-class laser sources devoted to attosecond physics." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX064/document.
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Cette thèse s’inscrit dans le cadre du développement d’une source laser TW, de cadence élevée, stabilisée en phase, et délivrant des impulsions de quelques cycles optiques pour explorer la physique attoseconde. De telles impulsions contiennent seulement quelques oscillations de l’onde porteuse (durée de 5 fs à une longueur d’onde centrale de 800 nm) et ne sont pas directement disponibles à la sortie d’une source laser femtoseconde classique. Une technique de post-compression efficace pour obtenir de telles impulsions consiste à élargir le spectre des impulsions laser par automodulation de phase dans une fibre creuse remplie de gaz, puis à compenser la phase spectrale introduite avec des miroirs chirpés. Cette technique convient à des impulsions dont l’énergie est inférieure au millijoule. Au-delà, la transmission et la stabilité du compresseur chutent fortement à cause d'effets non linéaires tels que l'autofocalisation et l'ionisation. Pour comprimer des impulsions énergétiques et dont la phase de l’enveloppe est stabilisée par rapport à la porteuse (stabilisation de la CEP), il est possible de diviser l'impulsion initiale en plusieurs répliques d'énergie moindre et de réduire ainsi l'intensité crête en entrée de fibre. Le spectre de chaque réplique est alors élargi indépendamment. Dans le cadre de cette thèse, la combinaison cohérente passive d'impulsions de quelques cycles optiques issues d'une fibre creuse remplie de gaz est démontrée pour la première fois. L'utilisation de lames biréfringentes (calcite) dont l’orientation est soigneusement déterminée permet de générer et combiner des répliques avec une efficacité élevée. Ainsi, dans le cas d’une division en deux répliques, des impulsions stabilisées en phase (CEP), de durée 6 fs et d'énergie 0.6 mJ ont été générées de manière fiable et reproductible. L’étude détaillée de cette technique, aussi bien théorique qu’expérimentale, a permis de mettre en évidence les conditions requises pour générer des impulsions de quelques cycles optiques et présentant un bon contraste temporel. Plus précisément, la phase spectrale relative entre les répliques peut être mesurée à l'aide d'une méthode interférométrique permettant de quantifier les déphasages résiduels dus à la lame qui recombine les répliques, ainsi que ceux induits lors de la propagation dans la fibre par d'éventuels effets de modulation de phase croisée ou d'ionisation. Les effets qui affectent le processus de combinaison des répliques, tels que les modifications des états de polarisation des répliques ou bien les interactions non linéaires entre les répliques, sont analysés en détail. Une méthode est proposée pour minimiser ces effets, même dans le cas plus critique de la division et combinaison d'impulsions à quatre répliquesThe framework of this thesis is the design and development of a TW-class, high-repetition rate, CEP-stabilized, few-cycle laser system devoted to attosecond physics. Few-cycle pulses includes only a few oscillations of the carrier wave (duration about 5 fs for 800nm central wavelength) and are not directly available at the output of typical femtosecond sources. One of the most popular techniques used for producing such pulses with high spatial quality is nonlinear spectral broadening in a gas-filled hollow-core fiber followed by temporal compression with chirped mirrors. However, as the input pulse energy approaches the milliJoule level, both the transmission and stability of hollow fiber compressors rapidly drop with the onset of self-focusing and ionization. A way of overcoming this limitation is to divide the input pulse into several lower energy replicas that can be subsequently recombined after independent spectral broadening in the fiber. In this thesis, the passive coherent combining of millijoule energy laser pulses down to few-cycle duration in a gas-filled hollow fiber is demonstrated for the first time. High combining efficiency is achieved by using carefully oriented calcite plates for temporal pulse division and recombination. Carrier-envelope phase (CEP)- stable, 6-fs, 800-nm pulses with more than 0.6 mJ energy were routinely generated in the case of twofold division and recombination. A detailed theoretical and experimental analysis of this temporal multiplexing technique is proposed to explain the conditions required for producing few-cycle pulses with high fidelity. In particular, an interferometric method for measuring the relative spectral phase between two replicas is demonstrated. This gives a measure of the phase mismatch in the combining plate, as well as that induced by eventual cross-phase modulation or ionization during propagation in the fiber. The effects degrading the combining process, as polarization change or nonlinear interactions between pulse replicas are analyzed in details. A method is proposed to overcome these limitations, even in the critical case of fourfold pulse division and combination
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Dubois, Jonathan. "Electron dynamics for atoms driven by intense and elliptically polarized laser pulses." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0297.
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Assujettir des atomes ou des molécules à des impulsions lasers de fortes intensités done lieu à une variété de phénomènes hautement non-linéaires, tels que par exemple l'ionisation des électrons et la radiation de photons de hautes fréquences. Les distributions des vitesses des électrons ionisés ou des fréquences des photons radiés encodent des informations pertinentes sur les atomes ou les molécules ciblés à l'échelle temporelle naturelle des électrons, l'attoseconde-qui est un millionième, d'un millionième, d'un millionième d'une seconde. Comprendre la dynamique des électrons ionisés ainsi qu'identifier les mécanismes de radiation de hautes fréquences sont des étapes essentielles afin d'interpréter et décoder les informations cryptées dans les mesures expérimentales.Dans cette thèse, des atomes soumis à des impulsions lasers de fortes intensités polarisées elliptiquement dans le régime infra-rouge sont étudiés théoriquement. Malgré leur nature fondamentalement quantique dans les atomes, les électrons manifestent certains comportements classiques lorsqu'ils sont sujets à des impulsions lasers de fortes intensités. Nous exploitons ces traits classiques pour comprendre et illustrer, à l'aide des trajectoires, les mécanismes physiques en jeu afin d'interpréter les résultats expérimentaux. Après ioniser, le mouvement des électrons est analysé en utilisant des techniques issues de la dynamique non-linéaire. Ce travail de thèse démontre la complémentarité de la mécanique quantique et de la dynamique non-linéaire pour comprendre et illustrer des mécanismes impliqués lorsque des atomes sont sujets à des impulsions lasers de fortes intensités polarisées elliptiquementSubjecting atoms or molecules to intense laser pulses gives rise to a variety of highly nonlinear phenomena, such as for instance the ionization of electrons and the radiation of high-frequency photons. The distributions of the velocity of the ionized electrons of the frequency of the radiated photons measured at the detector encode relevant informations on the target atoms and molecules at the natural time scale of the electrons, the attosecond-that is, million, million, millionths of a second. Understanding the dynamics of the ionized electrons and identifying the mechanisms of high-frequency radiation are essential steps toward interpreting and decoding the informations encrypted in the experimental measurements.In this thesis, atoms subjected to intense and elliptically polarized laser fields in the infrared regime are theoretically studied. Despite their fundamental quantal nature in atoms, electrons display some classical behaviors when subjected to intense laser pulses. We exploit these classical features to understand and picture, with the help of trajectories, the physical mechanisms at play in order to interpret experimental measurements. After ionizing, the motion of the electrons is analyzed using techniques from nonlinear dynamics. This thesis work demonstrates the complementarity of quantum mechanics and nonlinear dynamics for understanding and illustrating the mechanisms involved when atoms are subjected to intense and elliptically polarized laser pulses
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Götz, Sebastian Reinhold [Verfasser], Tobias [Gutachter] Brixner, Bert [Gutachter] Hecht, and Björn [Gutachter] Trauzettel. "Nonlinear spectroscopy at the diffraction limit: probing ultrafast dynamics with shaped few-cycle laser pulses / Sebastian Reinhold Götz ; Gutachter: Tobias Brixner, Bert Hecht, Björn Trauzettel." Würzburg : Universität Würzburg, 2019. http://d-nb.info/120085635X/34.
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Wang, Jin. "Ultrafast studies of reactive intermediates." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196155202.
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Bain, Fiona Mair. "Yb:tungstate waveguide lasers." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1698.
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Lasers find a wide range of applications in many areas including photo-biology, photo-chemistry, materials processing, imaging and telecommunications. However, the practical use of such sources is often limited by the bulky nature of existing systems. By fabricating channel waveguides in solid-state laser-gain materials more compact laser systems can be designed and fabricated, providing user-friendly sources. Other advantages inherent in the use of waveguide gain media include the maintenance of high intensities over extended interaction lengths, reducing laser thresholds. This thesis presents the development of Yb:tungstate lasers operating around 1μm in waveguide geometries. An Yb:KY(WO₄)₂ planar waveguide laser grown by liquid phase epitaxy is demonstrated with output powers up to 190 mW and 76 % slope efficiency. This is similar to the performance from bulk lasers but in a very compact design. Excellent thresholds of only 40 mW absorbed pump power are realised. The propagation loss is found to be less than 0.1 dBcm⁻¹ and Q-switched operation is also demonstrated. Channel waveguides are fabricated in Yb:KGd(WO₄)₂ and Yb:KY(WO₄)₂ using ultrafast laser inscription. Several of these waveguides lase in compact monolithic cavities. A maximum output power of 18.6 mW is observed, with a propagation loss of ~2 dBcm⁻¹. By using a variety of writing conditions the optimum writing pulse energy is identified. Micro-spectroscopy experiments are performed to enable a fuller understanding of the induced crystal modification. Observations include frequency shifts of Raman lines which are attributed to densification of WO₂W bonds in the crystal. Yb:tungstate lasers can generate ultrashort pulses and some preliminary work is done to investigate the use of quantum dot devices as saturable absorbers. These are shown to have reduced saturation fluence compared to quantum well devices, making them particularly suitable for future integration with Yb:tungstate waveguides for the creation of ultrafast, compact and high repetition rate lasers.
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Friedman, Melissa E. "Pulse shaping for broadband photoassociation of cold molecules." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:18d49cc2-9146-4ff8-b3b3-9e045bff039c.
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The development of the field of the science of ultra-cold matter has opened some exciting possibilities in exploring the quantum-mechanical processes which dominate matter interactions at the sub-microscopic scale. Although methods of cooling atoms are well established, molecular cooling is made difficult by molecules’ additional vibrational and rotational degrees of freedom. It was the goal of the research in this work to approach molecular cooling indirectly, by using broadband shaped-pulse photoassociation for the generation of tightly bound ultracold Rb2 molecules. The experiments towards this goal conducted by our group included a pumpdecay experiment to observe the generation of ground state singlet or triplet molecules. However, attempts to observe an increase in ground state population have been unsuccessful. A pump-probe study of wavepacket dynamics in the 5s+5p electronic state was conducted in order to determine the appropriate timing for the application of an additional pulse to dump population into the ground state. Although the attempt to observe wavepacket oscillations has been unsuccessful, pump-probe studies have yielded the observation of loosely bound excited state molecules as a result of the photoassociation pulse. These results are promising as a first stage in a fully coherent pump-dump approach to stabilisation into the lowest vibrational ground state. This thesis will provide an introduction and overview to the concerns involved in addressing the problem of molecular cooling and generation. Experimental techniques will be discussed including pulsed laser systems, optical parametric amplifi- cation, and the presentation of an original design for pulse shaping with an acoustooptic modulator. The emphasis of these discussions will be on the principles and operating procedures required for the use of these devices as home-built systems. The thesis will conclude with the results of pump-probe experiments utilising the pulse shaper as a spectral cutting device.
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Meyer, Rémi. "Contrôle du dépôt d'énergie par laser femtoseconde dans les diélectriques par faisceaux de Bessel : profil spatio-temporel de densité plasma et applications au clivage du verre." Thesis, Bourgogne Franche-Comté, 2020. http://indexation.univ-fcomte.fr/nuxeo/site/esupversions/9cca4761-0970-4b3d-a6e9-01b766feff4d.
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L'utilisation d'impulsions ultrabrèves pour l'usinage laser permet une grande précision du dépôt d'énergie grâce à un fort confinement de l'interaction laser-matière. Les effets non-linéaires liés à ce confinement sont aussi usuellement responsables de distorsions et d'instabilités dans le profil d'intensité lors de la propagation. Les faisceaux de Bessel à hauts angles coniques ont démontré être très performants pour l'usinage des diélectriques grâce à leur robustesse aux effets non-linéaires. En régime femtoseconde, ils permettent alors de générer dans les milieux transparents des nanocanaux à haut rapport de forme par tirs uniques dans les milieux transparents. Cependant la dynamique d'ablation et le couplage de l'impulsion avec le plasma induit sont encore peu compris dans ce cadre, et le modèle courant les décrivant reste incompatible avec les observations expérimentales. Cette thèse a pour objectif d'étudier cette interaction et se divise en deux axes de travail. Le premier axe porte sur la caractérisation de l'interaction laser-matière dans les milieux transparents pour le cas des faisceaux de Bessel femtoseconde grâce au développement et à l'exploitation d'une expérience pompe-sonde interférométrique. Nous mesurons la dynamique du plasma via les modifications d'indice de réfraction qu'il induit, résolues dans le temps et l'espace. Les résultats préliminaires obtenus montrent que le plasma est confiné dans un rayon inférieur à un micron et que la densité du plasma approche de la densité critique pour une énergie proche du seuil de formation de nanocanaux. Dans un second axe, nous travaillons sur l'effet d'un alignement de nanocanaux sur la fracture d'échantillons de verre et les applications des faisceaux de Bessel pour le clivage du verre. Nous levons ici deux limites principales concernant la qualité de fracture, en optimisant le profil spatial du faisceau. Nous montrons que l'utilisation de faisceaux de Bessel elliptiques améliore considérablement la qualité de clivage pour les plaques de verre minces (150 µm), et nous établissons une preuve de principe de clivage du verre de grande épaisseur (10 mm) en un seul passage sous le laser grâce à l'utilisation d'un dispositif composé de 3 axiconsThe use of ultrashort pulses for laser ablation allows for a precise energy deposition thanks to a highly confined laser-matter interaction. The non-linear effects causing this confinement are also usually responsible of beam profile distorsions along propagation and intensity instabilities. High cone angle Bessel beams have shown to be excellent candidates for dielectrics processing since they are robust to non-linear effects. In femtosecond regime, they are able to generate in single shot high aspect ratio nanochannels in transparent media. However the ablation dynamics and the coupling with the laser-induced plasma remain partially unclear in this case. The current model describing such interaction is uncompatible with experimental observations. This thesis investigates the laser-plasma interaction and follows two axes of work. First part is focused on the laser-plasma interaction characterization in transparent media and in the case of femtosecond Bessel beam, by developping and exploiting an interferometric pump-probe experiment. We measure the plasma dynamics through the plasma-related complex refraction index modifications, which we resolve in space and time. Preliminary results show a confined plasma (radius < 1 µm) in the transverse direction and whose density approaches the critical density for a pulse energy approaching the nanochannel formation threshold. In a second part, we investigate the effect of aligned nanochannels on the fracture ability of glass samples and its application to glass cleaving. Here we solve two limiting problems to high quality cleaving by spatial beam shape engineering: we demonstrate a signification improvement of 150 µm-thin glass cleaving by the use of elliptical-core Bessel beams; and we establish a proof of principle of 10 mm-thick glass single-pass cleaving thanks to a 3 axicons-based setup
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Resan, Bojan. "DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2907.
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A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.Ph.D.
Other
Optics and Photonics
Optics
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Bowlan, Pamela. "Measuring the spatiotemporal electric." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28188.
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Thesis (M. S.)--Physics, Georgia Institute of Technology, 2009.Committee Chair: Rick Trebino; Committee Member: Jennifer Curtis; Committee Member: John Buck; Committee Member: Mike Chapman; Committee Member: Stephen Ralph.
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Shimotsuma, Yasuhiko. "Nano-modification of transparent materials using ultrafast pulse laser." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144535.
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Kauer, Matthias. "Ultrafast dynamics and propagation of femtosecond pulses in semiconductor lasers." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621970.
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MacDonald, Kevin Francis. "Nonlinear optics of light-induced structural transitions in confined Gallium." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/428199/.
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Stoian, Razvan. "Adaptive techniques for ultrafast laser material processing." Habilitation à diriger des recherches, Université Jean Monnet - Saint-Etienne, 2008. http://tel.archives-ouvertes.fr/tel-00352662.
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Le besoin d'une très grande précision lors du traitement des matériaux par laser a fortement encouragé le développement des études de l'effet des impulsions ultra brèves pour la structuration des matériaux à une échelle micro et nano métrique. Une diffusion d'énergie minimale et une forte non linéarité de l'interaction permet un important confinement énergétique à des échelles les plus petites possibles. La possibilité d'introduire des changements de phases rapides et même de créer de nouveaux états de matière ayant des propriétés optimisées et des fonctions améliorées donne aux impulsions ultra brèves de sérieux arguments pour être utilisées dans des dispositifs très précis de transformation et de structuration des matériaux. L'étude de ces mécanismes de structuration et, en particulier, de leurs caractéristiques dynamiques, est une clé pour l'optimisation de l'interaction laser-matière suivant de nombreux critères utiles pour les procédés laser : efficacité, précision, qualité. Ce mémoire synthétise les travaux de l'auteur sur l'étude statique et dynamique du dépôt d'énergie ultra rapide, avec application aux procédés laser. La connaissance de la réponse dynamique des matériaux après irradiation laser ultra brève montre que les temps de relaxation pilotent l'interaction lumière-matière. Il est alors possible d'adapter l'énergie déposée à la réponse du matériau en utilisant les toutes récentes techniques de mise en forme spatio temporelle de faisceaux. Un couplage optimal de l'énergie donne la possibilité d'orienter la réponse du matériau vers un résultat recherché, offrant une grande flexibilité de contrôle des procédés et, sans doute, la première étape du développement de procédés « intelligents ».
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Miura, Kiyotaka. "Studies on Modification of Glass Structure Using Ultrafast Pulse Laser." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/77753.
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Nguyen, Dat. "Dynamic feedback pulse shaping for high power chirped pulse amplification system." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5826.
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The topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic pulse shaping approaches. The experimental research addresses the topic of parabolic pulse generation in two distinct ways. First, pulse shaping technique involving a time domain approach is presented, that results in stretched pulses with parabolic profiles with temporal duration of 15 ns. After pulse is shaped into a parabolic intensity profile, the pulse is compressed with DCF fiber spool by 100 times to 80 ps duration at FWHM. A different approach of pulse shaping in frequency domain is performed, in which a spectral processor based on Liquid Crystal on Silicon technology is used. The pulse is stretched to 1.5 ns before intensity mask is applied, resulting in a parabolic intensity profile. Due to frequency to time mapping, its temporal profile is also parabolic. After pulse shaping, the pulse is compressed with a bulk compressor, and subsequently analyzed with a Frequency Resolved Optical Gating (FROG). The spectral content of the compressed pulse is feedback to the spectral processor and used to adjust the spectral phase mask applied on the pulse. The resultant pulse after pulse shaping with feedback mechanism is a Fourier transform, sub-picosecond ultrashort pulse with 5 times increase in peak power. The appendices in this dissertation provide additional material used for the realization of the main research focus of the dissertation. Specification and characterization of major components of equipment and devices used in the experiment are present. The description of Matlab algorithms that was used to calculate required signals for pulse shaping are shown. A brief description of the Labview code used to control the spectral processor will also be illustrated.Ph.D.
Doctorate
Physics
Sciences
Physics
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Kakkar, Tarun. "Ultrafast pulsed laser plasma fabrication of erbium doped thin film sensors." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19145/.
Full textAbstract:
Erbium (Er3+) ions have been extensively used in the field of integrated photonics due to it's characteristic fluorescence properties which can be used to amplify the optical signal in fibre based optical communication systems. In this study, novel materials were developed by doping Er3+ ions in glass polymer (GP) superlattice coated on a silicon substrate to investigate its application as an infrared (IR) sensor. The conventional IR detectors are classified as thermal detector and photonic detectors. The conventional photonic detector has better sensing capabilities however, they are required to be cooled down to 77 K for sensing IR radiations. Thus the current requirement is to develop uncooled IR detector which can sense minute changes in the temperature. The initial studies show that GP superlattice coated tipless cantilevers are able to sense changes in temperature with a resolution of 2 mK per nm deflection of the cantilever. The second part of the study was to dope Er3+ ions with or without Ytterbium (Yb3+) ions as a co-dopant in fused silica for glucose sensing. The fabrication was done using the pulsed laser deposition method which is a well-established technique for manufacturing nanoengineered thin films. The parameters for fabrication of optical glucose sensor were altered to assess the impact of different parameters such as chamber oxygen pressure, deposition time, Er3+ and Yb3+ ions concentrations on structural and fluorescence characteristics of thin films. The spectroscopic characterisation revealed that the low doping (0.25 mol %) concentration of Er3+ ions in the thin films results in longer fluorescence lifetime of up to 12.4 ms while the doping of Er3+ ion in fused silica has been achieved to 2.4 micron depth. The fabricated thin films were also characterized using techniques such as absorption spectroscopy, fluorescence spectroscopy, prism coupling, energy dispersive x-ray mapping using transmission electron microscopy. The thin films with longer fluorescence lifetime were selected for glucose monitoring device development. Poor management of diabetes mellitus can result in various complications such as cardiovascular disease, retinopathy, neuropathy and limb amputations. Diabetes control and complication trial highlighted that, with better glycaemic control resulted in reduced complications due to diabetes. The current techniques available to measure glucose levels are invasive in nature. Presently there is a desperate need for non-invasive sensing technology which is considered as holy grail for glycaemic control. The glucose sensing capabilities of the Er3+ ions doped fused silica was tested using in-vitro glucose measurement in aqueous solutions, blood samples, and intralipids solution. A laboratory bench prototype was developed for a pilot clinical study on people with type 1 diabetes. The change in fluorescence lifetime due to change in glucose concentrations was analysed. The calibrated values were then correlated with the actual glucose reading from finger prick handheld glucose meter and invasive continuous glucose monitor (ICGM). The results were analysed using clarke error grid (CEG) analysis which is a standard statistical analysis tool to assess the accuracy of the device. The next stage of the development includes fabricating a new batch of the photonics chips which has shown the glucose sensing capabilities and thereafter carrying out in-vitro testing as well as carry out the second stage of clinical trials.
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Wu, Yi. "High flux isolated attosecond pulse generation." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6038.
Full textAbstract:
This thesis outlines the high intensity tabletop attosecond extreme ultraviolet laser source at the Institute for the Frontier of Attosecond Science and Technology Laboratory.
First, a unique Ti:Sapphire chirped pulse amplifier laser system that delivers 14 fs pulses with 300 mJ energy at a 10 Hz repetition rate was designed and built. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two stage Ti:Sapphire chirped pulse power amplifier with mJ-level white light pulses from a gas filled hollow core fiber. It is the highest energy level ever achieved by a broadband pulse in a chirped pulse amplifier up to the current date.
Second, using this laser as a driving laser source, the generalized double optical gating method is employed to generate isolated attosecond pulses. Detailed gate width analysis of the ellipticity dependent pulse were performed. Calculation of electron light interaction dynamics on the atomic level was carried out to demonstrate the mechanism of isolated pulse generation.
Third, a complete diagnostic apparatus was built to extract and analyze the generated attosecond pulse in spectral domain. The result confirms that an extreme ultraviolet super continuum supporting 230 as isolated attosecond pulses at 35 eV was generated using the generalized double optical gating technique. The extreme ultraviolet pulse energy was ~100 nJ at the exit of the argon gas target.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Patel, Aabid. "Phenomena of ultrafast laser material modification with respect to spatio-temporal couplings of the laser pulse." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/415994/.
Full textAbstract:
The nano-structuring of transparent media with subpicosecond laser pulses has attracted significant interest due to its unique applications. In contrast to nanosecond pulses where the energy introduced to the lattice is absorbed, leading to melting/boiling of the material around the focal volume, femtosecond lasers can alter material properties of the glass at high pressures without excessive production of heat, modifying the structures with sub-micron resolution. Permanent modifications can then be induced without strong collateral damage. Although femtosecond pulses are beneficial for material processing, short pulse durations and broad spectral bandwidths require a novel approach to femtosecond pulse control. It is well known that laser induced modification depends on fluence, wavelength and polarization. Another dependence of material modification is the spatio-temporal properties of the ultrashort pulse. These spatio-temporal couplings give rise to intrinsic nonlinear optical phenomena, which are well known in experiment but otherwise lack a clear explanation. While the formation mechanisms with respect to the nano-structuring of transparent media is still under debate, a better understanding of the nonlinear optical phenomena that affects the formation would provide insight into the physics of ultrafast light-matter interaction. In this thesis, the origin and thorough investigation of spatio-temporal induced phenomena are reported. By controlling the spatio-temporal couplings separately, I demonstrate complete control of all of the dependencies with the use of prism compressors and grating compressors and discuss the intricacies behind the control of the spatio-temporal couplings with complete characterization of the pulse. By investigating two of the main phenomena associated with spatio-temporal couplings, which give rise to a directional dependence when writing in the bulk (“quill-writing effect”) and a photosensitive anisotropy (“blade effect”), a more thorough understanding of the light-matter interaction is demonstrated and reported. I demonstrate that spatio-temporal couplings are inherent for all ultrafast laser systems with chirped-pulse amplification and result in a strongly anisotropic light-matter interaction. I identify angular dispersion in the focus as the main cause for the anisotropic photosensitivity coming from the spatially chirped pulse, which shows to yield a 200% increase in modification strength. With tighter focusing (NA ≥ ~0.4), this non-paraxial effect leads to a more apparent manifestation of spatio-temporal couplings in photo-induced modification. I control the anisotropy and exploited it as a new degree of freedom in tailoring laser induced modification in transparent material. A non-paraxial field structure analysis near the focus is conducted, with an elliptical optical beam, to provide insight on the origin of the photosensitive anisotropy. After a complete identification of the spatio-temporal properties of the electric field, the quill-effect was confirmed to be due to pulse front tilt in the focus with a direct comparison with other major spatio-temporal couplings including wavefront rotation. I reveal that the non-reciprocity during femtosecond laser writing in transparent media induces either an isotropic damage-like structure or a self-assembled nanostructure depending on the movement direction of the beam - known as the “quill-writing effect.” I also identify the switching of the modification regime from the formation of isotropic damage-like to anisotropic grating-like structures observed when the translation of the beam is in the direction of the tilt and is qualitatively described in terms of the first-order phase transition in the irradiated volume of a transparent dielectric. The structural evolution from void modification to self-assembled nanogratings in fused silica for moderate (NA > 0.4) focusing conditions is also discussed in this thesis. Void formation appears before the geometrical focus after the initial few pulses with nanogratings gradually occurring at the top of the induced structures after subsequent irradiation. Nonlinear Schrödinger equation-based simulations are conducted to simulate the laser fluence, intensity and electron concentration in the regions of modification. Comparing the experiment with simulations, the voids form due to cavitation in the regions where electron concentration exceeds 1020 cm-3 but remains below critical. In this scenario, the energy absorption is insufficient to reach the critical electron concentration that was once assumed to occur in the regime of void formation and nanogratings, shedding light on the potential formation mechanism of nanogratings. In-situ observations of harmonic generation during the ultrafast laser writing is presented to better understand the underlying physics that occur during the process of nanograting formation. Second and third harmonic generation is observed, with third harmonic distributed as two lobes following the polarization orientation of the electric field, identified as Cherenkov Third Harmonic. These harmonics are observed and correlated with the different regimes of material modification to understand whether they are part of the nanograting formation or corollary to give insight on the formation mechanisms of the self-assembled nanostructures. Finally, I discuss the work on the concept of an on-axial simultaneous spatio-temporal focusing with the use of a simple polarization dependent circular grating for the purpose of material modification using the expertise of the group on polarization gratings. The design and theoretical validation of the technique is reported in this thesis with the potential of further work in perfecting it for material modification and chirped-pulse amplification applications.