Dissertationen zum Thema „Pulsed laser system“
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1
Dulgergil, Ebru. „Development Of A Pulsed Fiber Laser For Ladar System“. Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614635/index.pdf.
Annotation:
In recent years laser technology has increasingly developed with the use of
fiber lasers and this has provided the possibility to implement different techniques in
the defense industry. LADAR is at the forefront of these techniques. Fiber lasers
constitute a perfect source for LADAR systems due to their excellent robustness,
compact size and high-power generation capability. In this study we will explore the
development of a pulsed fiber laser source for a LADAR system that can obtain high
resolution 3D images in eye-safe region.
A high power, all fiber integrated erbium system with strictly single mode
operation in eye-safe region based on MOPA (master oscillator power amplifier)
configuration with seed source and amplifier part was developed. Both the use of an
actively mode locked laser with erbium doped fiber and fiber coupled modulated
distributed feedback diode laser were investigated as seed sources for the amplifier
part. Both erbium doped single clad fiber and erbium-ytterbium doped double clad
gain fiber were used in this amplifier system. After amplification of the actively
mode locked laser, 12 W of average optical power was obtained through single
mode fiber with 1ns pulse duration at 10 MHz which corresponds to 1.2 kW peak
power. For the fiber coupled DFB diode laser, 9.5W average power was obtained
with around 8 ns duration pulses at 100 kHz and about 9.2 W average power was
also obtained with around 700 ps duration pulses at 1 MHz through strictly single
mode fiber at the output of the same amplifier system as was used in the actively
mode locked seed source. In both cases calculated peak power was around 10 kW
v
which is estimated as the highest peak power for an all fiber integrated system with
single mode operation.
The development of such a fiber system with high power capability, compact
size and free of misalignment is expected to be useful for LADAR application as
well as other areas such as eye surgery, 3D silicon processing or any other material
processing applications.
2
Ghose, Abhijit. „Pulsed measurement based nonlinear characterization of avalanche photodiode for the time error correction of 3D pulsed laser radar“. Kassel Kassel Univ. Press, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2709432&prov=M&dok_var=1&dok_ext=htm.
3
Yagci, Mahmut Emre. „Development Of A Picosecond Pulsed Mode-locked Fiber Laser“. Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615773/index.pdf.
Annotation:
Fiber lasers represent the state-of-the-art in laser technology and hold great promise for a
wide range of applications because they have a minimum of exposed optical interfaces,
very high efficiency, and are capable of exceptional beam quality. In the near future, the
most important markets such as micromachining, automotive, biomedical and military
applications will begin to use this technology. The scope of this thesis is to design and
develop a short picosecond pulsed fiber laser using rare-earth doped fiber as a gain
medium. The proposed master oscillator power amplifier (MOPA) will be used to generate
pulses with high repetition rates.
In this study, first we explain the basic theoretical background of nonlinear optics and fiber
laser. Then, the numerical simulation will be introduced to explain how the laser system
design and optimization. The simulation is based on nonlinear Schrödinger equation with the method of split-step evaluation. The brief theoretical background and simulation results of the laser system will be shown. Finally, the experimental study of the developmental fiber laser system that comprises an oscillator, preamplifier and power amplifier will be discussed.
4
Patel, Sunil. „A chirped, pulsed laser system and magneto-optical trap for rubidium“. Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/66245/.
Annotation:
This thesis covers the construction and characterisation of a magneto-optical trap (MOT) for 85Rb from the very beginning. It details both the optical and mechanical aspects from laser diode assembly, tuning and stabilisation to the preparation and assembly of the vacuum system. The MOT construction forms the first goal of the project, the second was to develop a laser system capable of producing custom programmable, amplitude modulated and frequency chirped pulses (on the tens of microseconds timescale) from a continuous wave source. This involved developing software and computer control for several arbitrary signal generators linked to drivers for acousto-optic and electro-optic modulators. This chirped, pulsed laser system will be used to perform state manipulations on the 85Rb MOT cloud using two-photon Raman transitions in an adiabatic rapid passage regime. The chirped pulse system was initially tested with a rubidium vapour cell in an attempt to perform atomic interferometry that would produce spatial interference fringes along the length of the cell. However, due to the beam power requirements, the beam diameter together with the large Doppler shift at room temperature meant these fringes were not seen and so the vapour cell was replaced with the cold atom cloud in the MOT. Two-photon experiments were attempted with the MOT cloud using the chirped pulse system, however despite greatly improved laser power and detection eficiency, the signal indicating ground state population transfer via a two-photon interaction was not seen. The results indicate that the hyperfine-ground state splitting frequency has been shifted due to the proximity of the ion pump magnet to the vacuum system. Presently, efforts are being directed towards searching for the correct frequency.
5
Jenderka, Marcus. „Pulsed Laser Deposition of Iridate and YBiO3 Thin Films“. Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-219334.
Annotation:
Die vorliegende Arbeit befasst sich mit dem Dünnfilmwachstum der ternären Oxide Na2IrO3, Li2IrO3, Y2Ir2O7 und YBiO3. All diesen oxidischen Materialien ist gemein, dass sie Verwirklichungen sogenannter Topologischer Isolatoren oder Spin-Flüssigkeiten sein könnten. Diese neuartigen Materiezustände versprechen eine zukünftige Anwendung in der Quantencomputation, in magnetischen Speichern und in elektrischen Geräten mit geringer Leistungsaufnahme. Die Herstellung der hier gezeigten Dünnfilme ist daher ein erster Schritt zur Umsetzung dieser Anwendungen in der Zukunft. Alle Dünnfilme werden mittels gepulster Laserplasmaabscheidung auf verschiedenen einkristallinen Substraten hergestellt. Die strukturellen, optischen und elektrischen Eigenschaften der Filme werden mittels etablierter experimenteller Verfahren wie Röntgenbeugung, spektroskopischer Ellipsometrie und elektrischenWiderstandsmessungen untersucht. Die strukturellen Eigenschaften von erstmalig in der Masterarbeit des Authors verwirklichten Na2IrO3-Dünnfilmen können durch Abscheidung einer ZnO-Zwischenschicht deutlich verbessert werden. Einkristalline Li2IrO3-Dünnfilme mit einer definierten Kristallausrichtung werden erstmalig hergestellt. Die Messung der dielektrischen Funktion gibt Einblick in elektronische Anregungen, die gut vergleichbar mit Li2IrO3-Einkristallen und verwandten Iridaten sind. Des Weiteren wird aus den Daten eine optische Energielücke von ungefähr 300 meV bestimmt. In Y2Ir2O7-Dünnfilmen wird eine mögliche (111)-Vorzugsorientierung in Wachstumsrichtung gefunden. Im Vergleich mit der chemischen Lösungsabscheidung zeigen die hier mittels gepulster Laserplasmaabscheidung hergestellten YBiO3-Dünnfilme eine definierte, biaxiale Kristallausrichtung in der Wachstumsebene bei einer deutlich höheren Schichtdicke. Über die gemessene dielektrische Funktion können eine direkte und indirekte Bandlücke bestimmt werden. Deren Größe gibt eine notwendige experimentelle Rückmeldung an theoretische Berechnungen der elektronischen Bandstruktur von YBiO3, welche zur Vorhersage der oben erwähnten, neuartigen Materiezuständen verwendet werden. Nach einer Einleitung und Motivation dieser Arbeit gibt das zweite Kapitel einen Überblick über den gegenwärtigen Forschungsstand der hier untersuchten Materialien. Die folgenden zwei Kapitel beschreiben die Probenherstellung und die verwendeten experimentellen Untersuchungsmethoden. Anschließend werden für jedes Material einzeln die experimentellen Ergebnisse dieser Arbeit diskutiert. Die Arbeit schließt mit einer Zusammenfassung und einem AusblickThe present thesis reports on the thin film growth of ternary oxides Na2IrO3, Li2IrO3, Y2Ir2O7 and YBiO3. All of these oxides are candidate materials for the so-called topological insulator and spin liquid, respectively. These states of matter promise future application in quantum computation, and in magnetic memory and low-power electronic devices. The realization of the thin films presented here, thus represents a first step towards these future device applications. All thin films are prepared by means of pulsed laser deposition on various single-crystalline substrates. Their structural, optical and electronic properties are investigated with established experimental methods such as X-ray diffraction, spectroscopic ellipsometry and resistivity measurements. The structural properties of Na2IrO3 thin films, that were previously realized in the author’s M. Sc. thesis for the first time, are improved significantly by deposition of an intermediate ZnO layer. Single-crystalline Li2IrO3 thin films are grown for the first time and exhibit a defined crystal orientation. Measurement of the dielectric function gives insight into electronic excitations that compare well with single crystal samples and related iridates. From the data, an optical energy gap of about 300 meV is obtained. For Y2Ir2O7 thin films, a possible (111) out-of-plane preferential crystal orientation is obtained. Compared to chemical solution deposition, the pulsed laser-deposited YBiO3 thin films presented here exhibit a biaxial in-plane crystal orientation up to a significantly larger film thickness. From the measured dielectric function, a direct and indirect band gap energy is determined. Their magnitude provides necessary experimental feedback for theoretical calculations of the electronic structure of YBiO3, which are used in the prediction of the novel states of matter mentioned above. After the introduction and motivation of this thesis, the second chapter reviews the current state of the science of the studied thin film materials. The following two chapters introduce the sample preparation and the employed experimental methods, respectively. Subsequently, the experimental results of this thesis are discussed for each material individually. The thesis concludes with a summary and an outlook
6
Thevar, Thangavel. „Design and development of a pulsed ruby laser system for an underwater holographic camera“. Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU065299.
Annotation:
This thesis presents a design of a ruby laser system which would form the heart of an underwater holographic camera. The design principally emphasised upon simplicity, compactness and lightweight construction, in addition to the achievement of the necessary coherence length. The research was mainly focused on Q-switching and longitudinal mode selection which were identified as the key elements in achieving our goal. A fresh insight into dye Q-switching was made with the view of its implementation in the laser. Two major experiments were carried out on a dye Q-switch consisting of cryptocyanine dye dissolved in methanol. The first trial explored the lifetime performance of the Q-switch with regards to the number of laser pulses fired and the elapsed time. It gave an indication of the suitability of this Q-switch for the application. The second experiment concentrated on evaluating the operational characteristics of a dye Q-switched ruby laser with regards to pump energy, dye absorbance, output energy and timing of the pulse emergence. The results of this experiment clearly defined the effects of variation of one parameter on another. Consequently, these results displayed in a number of graphical plots could form the basis for the selection of optimum parameters for such lasers. In addition to its primary role of creating a giant pulse, the performance of a Q-switch could be optimised or modified to enhance the longitudinal mode selection property of a laser. The mode selection properties of Pockels cell and dye Q-switched ruby lasers were theoretically developed before experimentally confirming the derived predictions to a good degree.
7
Ren, Lan. „Integrated process planning for a hybrid manufacturing system“. Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Ren_09007dcc8046714a.pdf.
Annotation:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 18, 2008) Includes bibliographical references.
8
Han, Sang-Choll. „Optimization of microwave excited CO2 laser system and generation of pulsed optical discharges in strong magnetic fields“. [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966063058.
9
Casbon, Michael Anthony. „Design and application of an advanced fully active harmonic load pull system using pulsed RF measurements and synchronised laser energy“. Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/115731/.
Annotation:
The objective of this work was to advance the design of Active Harmonic Load-Pull systems to facilitate accurate modelling of RF semiconductors, with specific regard to time dependant behaviours. Pulse capability is added, to extend the thermally safe operating region, investigate thermal behaviour, and reduce the thermal loading on the system components. The safe operation region extension is demonstrated with a GaAs die, the thermal aspects of behaviour are illustrated with GaN on SiC, GaN on Si and GaN on diamond die. A violet laser is added, which releases some types of trapped charge, helping to reveal the full potential of the device. The thermal transient response of the device is thereby exposed, and the trap filling times may be studied. The application of this to GaN die with and without Source Coupled Field Plates is described. The relevance of the light wavelength is briefly investigated. A novel wafer probe station is described, providing access to the backside of the wafer for photonic trap release and the measurement of hot electron electroluminescence, as RF measurements are conducted on the front side. Replacing the drain RF and DC circuits with a fixed resistor, and stepping the gate voltage allows the device to be held at any point on the load-line and then moved to another, here this demonstrates that the residual “knee-walkout” on a GaN on SiC part with an optimised source coupled field plate is not a thermal effect, and must therefore be due to trapped charge, despite the field plate. A low loss diplexer/ bias tee combination with very good DC supply memory properties is described, demonstrated with a InAlN/GaN die at Ka band. Accurate measurement of harmonics is vital to waveform engineering. Here a novel method of increasing the effective dynamic range of the system is presented.
10
Lin, Wenzhi. „Growth and Scanning Tunneling Microscopy Studies of Magnetic Films on Semiconductors and Development of Molecular Beam Epitaxy/Pulsed Laser Deposition and Cryogenic Spin-Polarized Scanning Tunneling Microscopy System“. Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1304610814.
11
Joblin, Anthony. „Resolution and contrast of a time domain transillumination breast imaging system“. Thesis, Queensland University of Technology, 1998.
12
Waroquet, Anne. „Couches-minces dans le système K-Nb-O : croissance épitaxiale et nanostructuration par PLD de phases pérovskite, TTB et lamellaires“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S143/document.
Annotation:
L'objectif de ce travail était l'élaboration par ablation laser pulsé (PLD) et la caractérisation de couches minces d'oxydes dans le système K-Nb-O, et plus précisément d'une phase de structure bronze de tungstène quadratique (TTB) sous forme de nanorods, potentiellement intéressante dans le contexte de la recherche de nouveaux piézoélectriques sans plomb. Malgré une forte compétition de croissance entre les différentes phases, l'étude approfondie des conditions de dépôt a montré la possibilité d'obtenir les phases KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB) et KNbO3, en films minces après une phase d’optimisation essentielle. Nous avons déterminé l'influence des conditions de dépôt sur la formation et la nanostructuration de ces composés en couches minces. En particulier, il a été démontré que la température et la composition de la cible PLD avaient une forte influence sur la croissance de la phase de structure TTB. Une étude plus approfondie de ces phases a révélé que toutes avaient une morphologie spécifique liée à leur structure anisotrope, que nous avons pu contrôler par la croissance épitaxiale sur les substrats SrTiO3 orienté (100) et (110). L'existence d'une activité piézoélectrique dans des couches minces de la phase TTB, mise en évidence par PFM, lui confère un intérêt certain. Cette phase TTB a également été obtenue dans le système Na-K-Nb-O, très connu pour ses propriétés piézoélectriques et ferroélectriques, ouvrant la voie sur de nouvelles recherchesThe purpose of this work was the elaboration by pulsed laser deposition (PLD) and the characterization of thin films of oxides in the K-Nb-O system, and more precisely that of a tetragonal tungsten bronze phase (TTB) as nanorods, of potential interest as a new lead free piezoelectric. In spite of a strong growth competition between the different phases, the detailed study of the deposition conditions showed that it is possible to obtain KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB ) and KNbO3 in thin films form after an important optimization step. We have determined the influence of these deposition conditions on the formation and the nanostructuration of these compounds as thin films. In particular, it was shown that the temperature and the PLD target’s composition has a strong influence on the growth of the TTB structure. A further study of these phases revealed that all have a specific morphology related to their anisotropic structure, that we have controlled by the epitaxial growth on the (100) and (110) SrTiO3 substrates. The existence of a piezoelectric activity in the TTB thin films, evidenced by PFM, gives a great interest to this phase. This TTB phase was also obtained in the Na-K-Nb-O system, well known for its piezoelectric and ferroelectric properties, opening the way to new research
13
Denis, Maxime. „Construction d'une expérience de Condensat de Bose-Einstein de 41K pour l'étude du rotateur frappé atomique“. Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR064.
Annotation:
Ce manuscrit présente la réalisation d'un dispositif expérimental permettant de produire des condensats de Bose-Einstein de potassium 41. Cette expérience a été construite dans le but d'étudier le modèle du rotateur frappé en présence d'interactions. Le choix du potassium 41 pour cette expérience est motivé par deux raisons. La première est que la longueur de diffusion de cet atome est positive (ce qui permet une condensation aisée) et qu'il possède des résonances de Feshbach accessibles. La seconde est que les longueurs d'ondes de ses transitions de refroidissement peuvent être générées par des sources lasers fibrées puissantes du domaine télécom doublées en fréquence. Cela a pour avantage de pouvoir fabriquer des systèmes lasers stables et robustes pour les étapes de refroidissement laser et de piégeage optique du potassium 41. La particularité de notre système réside dans la génération de fréquence qui a lieu en amont des étapes d'amplification à haute puissance et de doublage en fréquence. Le développement de ces bancs lasers agissant sur les deux transitions de refroidissement D1 et D2 a permis de mener à bien les étapes de refroidissement laser. Grâce à ces bancs lasers, un piège magnéto-optique rassemblant 3x10^(9) atomes a été obtenu. La compression et le refroidissement avec une mélasse grise de ce piège magnéto-optique a permis d'atteindre une température de 16 µK et une densité dans l'espace des phases de 10^(-6). Les étapes de refroidissement évaporatif qui suivent sont réalisées successivement avec un piège quadrupolaire, un piège hybride (piège quadrupolaire + piège optique) et pour terminer un piège optique croisé. Des condensats de 500 000 atomes ont été observés dans ce piège optique croisé. Nous avons aussi identifié des résonances de Feshbach qui permettront le contrôle des interactions. Pour l'étude du rotateur frappé, un système laser pulsé original a été conçu en parallèle. La réalisation de ce système a été faite à partir d'un laser pulsé télécom amplifié à haute puissance doublé en fréquence. Ce système produit des pulses laser proches infrarouge avec des impulsions de 10 ns, une fréquence de répétition comprise entre 100 kHz et 500 kHz et une puissance crête optique allant jusqu'à 350W. Ce banc laser pulsé nous a permis de réaliser les premières expériences du rotateur frappé de cette expérience. Un contrôle des interactions avec les résonances de Feshbach identifiées nous permettra d'étudier par la suite le modèle du rotateur frappé en présence d'interactionsThis manuscript presents the realization of an experimental device to produce Bose-Einstein condensates of potassium 41. This experiment was built to study the model of the kicked rotor in the presence of interactions. The choice of potassium 41 for this experiment is motivated by two reasons. The first is that the diffusion length of this atom is positive (allowing easy condensation) and has accessible Feshbach resonances. The second is that the wavelengths of its cooling transitions can be generated by powerful fiber laser sources in the telecom domain doubled in frequency. This has the advantage of being able to manufacture stable and robust laser systems for laser cooling and optical trapping of potassium 41. The particularity of our system lies in the frequency generation that takes place before the high power amplification and frequency doubling stages. The development of these laser benches acting on the two cooling transitions D1 and D2 enabled the laser cooling stages to be completed. Thanks to these laser benches, a magneto-optical trap gathering 3x10^(9) atoms was obtained. Compression and cooling with grey molasses of this magneto-optical trap allowed to reach a temperature of 16 µK and a density in the space of phases of 10^(-6). The following evaporative cooling steps are carried out successively with a quadrupolar trap, a hybrid trap (quadrupolar trap + optical trap) and to finish a crossed optical dipole trap. Condensates of 500,000 atoms were observed in this crossed optical dipole trap. We also identified Feshbach resonances that will allow the control of interactions. For the study of the kicked rotor, an original pulsed laser system was designed in parallel. The realization of this system was made from a high-power amplified telecom pulsed laser doubled in frequency. This system produces near infrared pulses at a repetition frequency between 100 kHz to 500 kHz with peak optical power up to 350W. This pulsed laser bench allowed us to perform the first experiments of the kicked rotor from this experiment. A control of the interactions with the identified Feshbach resonances will allow us to study the model of the kicked rotor in the presence of interactions
14
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.
Annotation:
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
15
MacFarlane, Duncan Leo. „Ultrashort Pulse Production in Synchronously Pumped Mode-Locked Dye Laser Systems“. PDXScholar, 1989. http://pdxscholar.library.pdx.edu/open_access_etds/1392.
Annotation:
The concern of this dissertation is the understanding and improvement of a class of lasers that is responsible for some of the shortest optical pulses available today. In particular, we seek ways to produce from synchronously pumped mode-locked dye laser systems, shorter pulses of higher intensity with improved pulse-to-pulse consistency. Specific topics.that are discussed herein include the study of the role of the pump pulse in synchronously pumped mode-locked lasers, the study of the pulse shaping and shortening due to an intracavity saturable absorber, and the study of a fundamental pulse train instability associated with these lasers.
16
Hornung, Thomas. „Optimal control with ultrashort laser pulses“. Diss., lmu, 2002. http://nbn-resolving.de/urn:nbn:de:bvb:19-2963.
17
Löser, Markus. „Diode-Pumped High-Energy Laser Amplifiers for Ultrashort Laser Pulses The PENELOPE Laser System“. Helmholtz-Zentrum Dresden - Rossendorf, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-232322.
Annotation:
The ultrashort chirped pulse amplification (CPA) laser technology opens the path to high intensities of 10^21 W/cm² and above in the laser focus. Such intensities allow laser-matter interaction in the relativistic intensity regime. Direct diode-pumped ultrashort solid-state lasers combine high-energy, high-power and efficient amplification together, which are the main advantages compared to flashlamp-pumped high-energy laser systems based on titanium-doped sapphire. Development within recent years in the field of laser diodes makes them more and more attractive in terms of total costs, compactness and lifetime.
This work is dedicated to the Petawatt, ENergy-Efficient Laser for Optical Plasma Experiments (PENELOPE) project, a fully and directly diode-pumped laser system under development at the Helmholtz–Zentrum Dresden – Rossendorf (HZDR), aiming at 150 fs long pulses with energies of up to 150 J at repetition rates of up to 1 Hz. The focus of this thesis lies on the spectral and width manipulation of the front-end amplifiers, trivalent ytterbium-doped calcium fluoride (Yb3+:CaF2) as gain material as well as the pump source for the final two main amplifiers of the PENELOPE laser system. Here, all crucial design parameters were investigated and a further successful scaling of the laser system to its target values was shown.
Gain narrowing is the dominant process for spectral bandwidth reduction during the amplification at the high-gain front-end amplifiers. Active or passive spectral gain control
filter can be used to counteract this effect. A pulse duration of 121 fs was achieved by using a passive spectral attenuation inside a regenerative amplifier, which corresponds to an improvement by a factor of almost 2 compared to the start of this work. A proof-of-concept experiment showed the capability of the pre-shaping approach. A spectral bandwidth of 20nm was transferred through the first multipass amplifier at a total gain of 300. Finally, the predicted output spectrum calculated by a numerical model of the final amplifier stages was in a good agreement with the experimental results.
The spectroscopic properties of Yb3+:CaF2 matches the constraints for ultrashort laser pulse amplification and direct diode pumping. Pumping close to the zero phonon line at 976nm is preferable compared to 940nm as the pump intensity saturation is significantly lower. A broad gain cross section of up to 50nm is achievable for typical inversion levels. Furthermore, moderate cryogenic temperatures (above 200K) can be used to improve the amplification performance of Yb3+:CaF2. The optical quality of the doped crystals currently available on the market is sufficient to build amplifiers in the hundred joule range.
The designed pump source for the last two amplifiers is based on two side pumping in a double pass configuration. However, this concept requires the necessity of brightness conservation for the installed laser diodes. Therefore, a fully relay imaging setup (4f optical system) along the optical path from the stacks to the gain material including the global beam homogenization was developed in a novel approach.
Beside these major parts the amplifier architecture and relay imaging telescopes as well as temporal intensity contrast (TIC) was investigated. An all reflective concept for the relay imaging amplifiers and telescopes was selected, which results in several advantages especially an achromatic behavior and low B-Integral. The TIC of the front-end was improved, as the pre- and postpulses due to the plane-parallel active-mirror was eliminated by wedging the gain medium.
18
Löser, Markus. „Diode-Pumped High-Energy Laser Amplifiers for Ultrashort Laser Pulses The PENELOPE Laser System“. Doctoral thesis, Helmholtz-Zentrum Dresden - Rossendorf, 2017. https://tud.qucosa.de/id/qucosa%3A30755.
Annotation:
The ultrashort chirped pulse amplification (CPA) laser technology opens the path to high intensities of 10^21 W/cm² and above in the laser focus. Such intensities allow laser-matter interaction in the relativistic intensity regime. Direct diode-pumped ultrashort solid-state lasers combine high-energy, high-power and efficient amplification together, which are the main advantages compared to flashlamp-pumped high-energy laser systems based on titanium-doped sapphire. Development within recent years in the field of laser diodes makes them more and more attractive in terms of total costs, compactness and lifetime.
This work is dedicated to the Petawatt, ENergy-Efficient Laser for Optical Plasma Experiments (PENELOPE) project, a fully and directly diode-pumped laser system under development at the Helmholtz–Zentrum Dresden – Rossendorf (HZDR), aiming at 150 fs long pulses with energies of up to 150 J at repetition rates of up to 1 Hz. The focus of this thesis lies on the spectral and width manipulation of the front-end amplifiers, trivalent ytterbium-doped calcium fluoride (Yb3+:CaF2) as gain material as well as the pump source for the final two main amplifiers of the PENELOPE laser system. Here, all crucial design parameters were investigated and a further successful scaling of the laser system to its target values was shown.
Gain narrowing is the dominant process for spectral bandwidth reduction during the amplification at the high-gain front-end amplifiers. Active or passive spectral gain control
filter can be used to counteract this effect. A pulse duration of 121 fs was achieved by using a passive spectral attenuation inside a regenerative amplifier, which corresponds to an improvement by a factor of almost 2 compared to the start of this work. A proof-of-concept experiment showed the capability of the pre-shaping approach. A spectral bandwidth of 20nm was transferred through the first multipass amplifier at a total gain of 300. Finally, the predicted output spectrum calculated by a numerical model of the final amplifier stages was in a good agreement with the experimental results.
The spectroscopic properties of Yb3+:CaF2 matches the constraints for ultrashort laser pulse amplification and direct diode pumping. Pumping close to the zero phonon line at 976nm is preferable compared to 940nm as the pump intensity saturation is significantly lower. A broad gain cross section of up to 50nm is achievable for typical inversion levels. Furthermore, moderate cryogenic temperatures (above 200K) can be used to improve the amplification performance of Yb3+:CaF2. The optical quality of the doped crystals currently available on the market is sufficient to build amplifiers in the hundred joule range.
The designed pump source for the last two amplifiers is based on two side pumping in a double pass configuration. However, this concept requires the necessity of brightness conservation for the installed laser diodes. Therefore, a fully relay imaging setup (4f optical system) along the optical path from the stacks to the gain material including the global beam homogenization was developed in a novel approach.
Beside these major parts the amplifier architecture and relay imaging telescopes as well as temporal intensity contrast (TIC) was investigated. An all reflective concept for the relay imaging amplifiers and telescopes was selected, which results in several advantages especially an achromatic behavior and low B-Integral. The TIC of the front-end was improved, as the pre- and postpulses due to the plane-parallel active-mirror was eliminated by wedging the gain medium.
19
Lomax, Andrew Martin. „Picosecond pulse control using semiconductor laser amplifiers“. Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333329.
20
Dupriez, Pascal. „Advanced high-power pulsed fibre laser systems and their applications“. Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/65498/.
Annotation:
In this thesis, I report experimental studies towards power scaling of ultrashort fibre-based sources designed for applications including high average power femtosecond pulse generation and nonlinear frequency conversion. While the power produced by rare-earth doped fibre lasers operating in continuous-wave has dramatically increased within a few years to exceed the kilowatt level, pulsed fibre sources have been limited to tens of watts due to the onset of nonlinearities in fibre amplifiers. Therefore the aim is to manage fibre nonlinearities to achieve specific output properties at high average power. An innovative aspect of this work lies in the remarkable combination of telecom-grade semiconductor laser sources and high-power Yb-doped fibre amplifier technologies to produce short pulses at very high average power. Fibre nonlinear effects are often detrimental to the performance of fibre systems but can also provide an attractive tool to generate new useful wavelengths. The final part of this thesis describes efficient white light generation produced by a microstructure fibre pumped by the previously described green fibre source. Furthermore, I investigated a novel fibre source configuration for guide star application. The source I developed produced 1W at 589 nm through frequency doubling of 1178 nm radiation produced by pulsed Raman amplification in an Yb-doped fibre amplifier.
21
Sullivan, Dustin L. Kovaleski Scott D. „Laser target triggering of gas switches“. Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/5670.
Annotation:
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 5, 2009). Thesis advisor: Dr. Scott Kovaleski. Includes bibliographical references.
22
Obozna, V. P., und О. S. Hnatenko. „Formation of Laser Radiation Pulses for Encoding inFormation“. Thesis, Sumy State University, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67954.
Annotation:
The main purpose of this work is to study the characteristics of the sequence of output pulses and the distances between the peaks of the pulses of the output radiation of a ring fiber femtosecond laser with nonlinear evolution of mode polarization for encoding information on the phase of pulses. An example of coding information for the phase of pulses is figure 1, which shows the pulse sequence corresponding to the number 101010010100 in the binary system, which is 2708 in the decimal system.
23
Röser, Fabian. „Power scaling of ultrashort pulse fiber laser systems“. Norderstedt Books on Demand GmbH, 2009. http://d-nb.info/1000542688/04.
24
Teh, Peh Siong. „High performance pulsed fiber laser systems for scientific & industrial applications“. Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/383623/.
Annotation:
This thesis reports an investigation of the power scaling of pulsed fiber laser systems towards the hundreds of Watts regime whilst keeping the impact of fiber nonlinearities such as Stimulated Raman Scattering (SRS) at a manageable level. Two regimes of pulsed operation are investigated: the nanosecond pulse regime and the picosecond pulse regime. Some of the work reported in this thesis was carried out in collaboration with SPI Lasers and Institute for Manufacturing, University of Cambridge under the TSB funded SMART LASER programme. In the nanosecond regime, two kinds of MOPA configurations are investigated. In the first instance a high accuracy active pulse shaping technique is implemented. Using the combination of a fast electrical Arbitrary Waveform Generator (AWG) and an Electro-Optic Modulator (EOM), optical pulses can be shaped into various custom defined pulse shapes with high temporal resolution feature definition, allowing faster pulse rise and fall times than previously possible. This MOPA has the capability to generate a maximum average output power of ~70 W, pulse energy close to 1 mJ, all within a diffraction limited output beam. The second instance a fully-fiberized system capable of producing up to 45 W of average output power with a pulse energy of ~1 mJ was developed in collaboration with SPI Lasers Ltd. Unlike the first system, which uses an EOM for optical pulse shaping, an Acousto-Optic Modulator (AOM) is instead used to pre-shape the leading edge of the optical seed pulse in order to reduce the impact of nonlinear effects caused by the high peak powers otherwise associated with gain-saturation assisted reshaping of long nanosecond square input pulses, providing a cost-effective solution for the SMART Laser system. The successful development of the SMART Laser system allowed SPI Lasers Ltd to introduce a new product line, namely the G4 pulsed fiber laser system. Both types of fiber laser system were used in material processing experiments to investigate their performance and capabilities. Using a nanosecond fiber MOPA as a pump source, a synchronously pumped, tuneable, Raman fiber laser is demonstrated both in the near infrared (NIR) and visible regions. A continuous tuning range of 28nm in the NIR and 2.8nm in the visible region are achieved with efficiencies in the range of 12% to 18% respectively. The conversion efficiency can be increased further with the use of a feedback signal. Furthermore, with the presence of a feedback signal, the linewidth of the Raman Stokes lines in both visible and NIR regions shows a significant narrowing effect. This technique will allow the generation of wavelengths which are not easily generated with rare-earth doped fiber lasers and will be useful in the fields of spectroscopy, archaeology, biomedical and many more. Next, optical pulses in the picosecond regime are investigated. A gain-switching technique is used to generate a stable train of picosecond optical pulses from a semiconductor laser diode (SLD). Gain switching of different types of commercially available SLDs shows different temporal and spectral characteristics which are primarily influenced by the design of the specific chip used. The shortest pulse durations achieved through direct gain switching resulted in ~50 ps pulses; however these were far from transform-limited. However, an external FBG seeded gain switched SLDs was shown to be capable of producing transform-limited optical pulses. I show that a mode-locking mechanism is responsible for the short, transform limited optical pulses observed. This is the first demonstration of a mode locked SLD at the 1.06 μm waveband. With this technique, 18 ps optical pulses with pulse energy of 7.2 pJ and peak power of 400 mW were obtained. The single polarization, stable, picosecond optical pulses were fed into a chain of polarization maintaining fiber amplifiers to investigate the power scaling capability of this system. A maximum average output power of 513 W is demonstrated in a diffraction-limited output beam. The system operated at a repetition frequency of 215 MHz, corresponding to an estimated pulse energy of 2.4 μJ and a peak power of ~ 69 kW. At the maximum operating output power, the OSNR is measured to be well above 26 dB with a polarization extinction ratio (PER) of 17 dB. A pulse energy of 3.23 μJ is achieved from a similar system at a reduced operating frequency of 53 MHz and an average optical power of 200 W, corresponding to a pulse peak power of 107 kW. In both cases, further power scaling is limited by the SRS. These results represent the highest optical power demonstrated from a fiber MOPA producing tens of picosecond optical pulses.
25
Mota, Alessandro Damiani. „Sistema eletrônico de controle para laser amarelo de aplicação oftalmológica com regime de operação contínuo e micro-pulsado“. Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-26042012-100723/.
Annotation:
Mais recentemente foi proposta uma nova técnica para tratamento de doenças relacionadas à retina humana, utilizando descargas laser na retina com seqüência de pulsos da ordem de 200 \'mü\'s, em substituição ao tratamento convencional que utiliza pulsos longos da ordem de 300 ms. A principal vantagem da nova técnica é a preservação (sem morte celular) do tecido exposto ao laser. Esse trabalho apresenta os mecanismos adotados para o desenvolvimento de um sistema eletrônico de controle de uma cavidade laser em 586 nm, para uso oftalmológico, que objetiva atender o protocolo exigido por essa técnica mais recente. O referido protocolo exige a formação de pulsos rápidos de laser, o que torna vital a velocidade do sistema eletrônico de controle da cavidade laser. Para atender os requisitos do projeto foram implementados dois controladores de corrente em malha fechada PI (Proporcional integrative controller) que trabalham em sincronismo, um controlador de potência óptica em malha fechada PI, e circuitos auxiliares de controle térmico da cavidade laser. Em software foram implementados um PI de potência, com objetivo de tornar a malha de controle estável com o tempo de resposta necessário, e o PI de controle térmico dos elementos da cavidade laser. Os testes realizados do protótipo demonstraram que o sistema de controle atendeu as especificações de projeto, principalmente no que se refere a tempo de resposta do pulso rápido, ponto fundamental na obtenção do protocolo clínico (FastPulse), que esse trabalho objetiva atender. Adicionalmente, o protótipo foi submetido a teste clínico em um paciente, e os resultados demonstraram eficácia no tratamento e ausência de marcas (lesões) na retina.Recently, scientists have proposed a new technique for treating diseases related to the human retina, which is based on retinal laser discharges using pulse sequence around of 200 \'mü\'s, replacing the conventional treatment using long pulses around of 300 ms. The main advantage of the new technique is the conservation (without cell death) of the area exposed to the laser. This work presents the mechanisms adopted for the development of an electronic control system of a laser cavity at 586 nm for ophthalmic use, which aims to meet the protocol required by this recent technique. The protocol requires the formation of rapid pulses of laser, which makes the electronic control system response velocity of the laser cavity vital to the protocol. To meet the project requirements were implemented two current controllers in closed loop PI (proportional integrative controller) working synchronized, an optical power controller in closed loop PI, and auxiliary circuits for temperature control of the laser cavity. Software were implemented for two controls, a PI power, in order to make the control loop stable with the required response time, and a PI thermal control for elements of the laser cavity. Tests showed that the prototype met the design specifications, especially regarding the response time of rapid pulse, key point in obtaining the clinical protocol (FastPulse), that this work aims to meet. Additionally, the prototype was subjected to clinical trial on a patient, and the results demonstrated efficacy and no visible lesions were noticed on retina.
26
Loeser, Markus. „Diode-Pumped High-Energy Laser Amplifiers for Ultrashort Laser Pulses“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-232571.
Annotation:
The ultrashort chirped pulse amplification (CPA) laser technology opens the path to high intensities of 10^21 W/cm² and above in the laser focus. Such intensities allow laser-matter interaction in the relativistic intensity regime. Direct diode-pumped ultrashort solid-state lasers combine high-energy, high-power and efficient amplification together, which are the main advantages compared to flashlamp-pumped high-energy laser systems based on titanium-doped sapphire. Development within recent years in the field of laser diodes makes them more and more attractive in terms of total costs, compactness and lifetime.
This work is dedicated to the Petawatt, ENergy-Efficient Laser for Optical Plasma Experiments (PENELOPE) project, a fully and directly diode-pumped laser system under development at the Helmholtz–Zentrum Dresden – Rossendorf (HZDR), aiming at 150 fs long pulses with energies of up to 150 J at repetition rates of up to 1 Hz. The focus of this thesis lies on the spectral and width manipulation of the front-end amplifiers, trivalent ytterbium-doped calcium fluoride (Yb3+:CaF2) as gain material as well as the pump source for the final two main amplifiers of the PENELOPE laser system. Here, all crucial design parameters were investigated and a further successful scaling of the laser system to its target values was shown.
Gain narrowing is the dominant process for spectral bandwidth reduction during the amplification at the high-gain front-end amplifiers. Active or passive spectral gain control
filter can be used to counteract this effect. A pulse duration of 121 fs was achieved by using a passive spectral attenuation inside a regenerative amplifier, which corresponds to an improvement by a factor of almost 2 compared to the start of this work. A proof-of-concept experiment showed the capability of the pre-shaping approach. A spectral bandwidth of 20nm was transferred through the first multipass amplifier at a total gain of 300. Finally, the predicted output spectrum calculated by a numerical model of the final amplifier stages was in a good agreement with the experimental results.
The spectroscopic properties of Yb3+:CaF2 matches the constraints for ultrashort laser pulse amplification and direct diode pumping. Pumping close to the zero phonon line at 976nm is preferable compared to 940nm as the pump intensity saturation is significantly lower. A broad gain cross section of up to 50nm is achievable for typical inversion levels. Furthermore, moderate cryogenic temperatures (above 200K) can be used to improve the amplification performance of Yb3+:CaF2. The optical quality of the doped crystals currently available on the market is sufficient to build amplifiers in the hundred joule range.
The designed pump source for the last two amplifiers is based on two side pumping in a double pass configuration. However, this concept requires the necessity of brightness conservation for the installed laser diodes. Therefore, a fully relay imaging setup (4f optical system) along the optical path from the stacks to the gain material including the global beam homogenization was developed in a novel approach.
Beside these major parts the amplifier architecture and relay imaging telescopes as well as temporal intensity contrast (TIC) was investigated. An all reflective concept for the relay imaging amplifiers and telescopes was selected, which results in several advantages especially an achromatic behavior and low B-Integral. The TIC of the front-end was improved, as the pre- and postpulses due to the plane-parallel active-mirror was eliminated by wedging the gain medium.
27
Takayanagi, Jun, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida und Toshio Goto. „Generation of high-power femtosecond pulse and octave-spanning ultrabroad supercontinuum using all-fiber system“. IEEE, 2005. http://hdl.handle.net/2237/6770.
28
Kim, Kyungbum. „ALL-SEMICONDUCTOR HIGH POWER MODE-LOCKED LASER SYSTEM“. Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2482.
Annotation:
The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.Ph.D.
Optics and Photonics
Optics
29
Mančal, Tomáš. „Laser pulse control of dissipative dynamics in molecular systems“. [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968759068.
30
Mancal, Tomas. „Laser pulse control of dissipative dynamics in molecular systems“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2002. http://dx.doi.org/10.18452/14895.
Annotation:
Diese Arbeit wird einer Weiterentwicklung der Dichtematrixtheorie und ihrer Anwendung zum Studium ultraschneller laserpulsinduzierter Dynamik in Molekularsystemen in Wechselwirkung mit einem thermischen Bad gewidmet. Zwei grosse Themenkomplexe werden behandelt. Zuerst werden die sogenannten Gedächtniseffekte diskutiert. Diese folgen aus einer reduzierten Beschreibung des Molekularsystems, in der die Umgebungsfreiheitsgrade eliminiert werden. Im zweiten Teil wird die Laserpulssteuerung der dissipativen Molekulardynamik untersucht. Die theoretische Beschreibung von offenen Quantensystemen führt zu einer zeitlich nicht-lokalen Bewegungsgleichung: Die Zeitentwicklung des Molekularsystems hängt von seiner Vergangenheit ab. In dieser Arbeit wird eine numerische Methode zur Lösung der zeitlich nicht-lokalen Bewegungsgleichung entwickelt und mit einem minimalen Modell eines polyatomaren Moleküls unter dissipativem Einfluss der Umgebung getestet. Eine analytische Lösung der Bewegungsgleichung für den speziellen Fall einer sehr langen Gedächtniszeit wurde hergeleitet. Zur Identifizierung solcher Gedächtniseffekte vergleichen wir diese analytische Lösung mit numerischen Rechnungen inklusive Gedächtnis und mit approximativen Rechnungen, die die zeitliche Nicht-Lokalität vernachlässigen. Für eine Anregung mit einem Laserpuls, der kürzer als die Gedächtniszeit des Systems ist, zeigt das Molekularsystem eine erkennbar unterschiedliche Dynamik als ohne Gedächtniss. Die Gedächtniseffekte werden mit abfallender Laserpulslänge deutlich ausgeprägter. Der zweite Teil der Arbeit konzentriert sich auf die Anwendung der Theorie der Optimalen Kontrolle, um die molekulare Dynamik zu steuern. Aus der Theorie der Optimalen Kontrolle erhält man Laserpulse, die bestimmte Aufgaben erfüllen, z.B. die Besetzung gewünschter vibronischer Niveaus des Molekularsystems oder die Platzierung eines Wellenpakets auf einer vorgegebenen Position auf der molekularen Potentialfläche. Als erstes Beispiel haben wir die Kontrolle des dissipativen fotoinduzierten Elektronentransfers in einem Donator-Brückenmolekül-Akzeptor System betrachtet, wobei wir das Gedächtniss vernachlässigt haben. Die Steuerbarkeit des Elektronentransfers wird diskutiert und der Mechanismus, mit dem sie möglich wird, wird identifiziert. Wir haben festgestellt, dass die Steuerung der Elektronentransferreaktionen selbst unter dem Einfluss von Dissipation möglich ist, obwohl die Kontrollausbeute mit steigender Dissipation drastisch abfällt. In Anwesenheit von Dissipation verändert sich auch der Mechanismus der Steuerung. Die experimentelle Ausführbarkeit der Herstellung des aus der Theorie der Optimalen Kontrolle resultierenden Kontrollpulses wird diskutiert und Methoden werden präsentiert, die die Abschätzung der Effizienz ermöglichen, mit der ein Flussigkristall--Laserpulsformer, wie er heute in Experimenten verwendet wird, den gewünschten Puls erzeugen kann. Um zwischen verschiedenen Kontrollaufgaben zu unterscheiden, wird ein quantitatives Mass eingeführt, das die Komplexität der Kontrollaufgabe charakterisiert. Die Theorie der Optimalen Kontrolle wird auch für Molekularsysteme formuliert, die statische Unordnung zeigen, und wird auf ein Ensemble von Molekülen mit zufälligen Orientierungen angewendet. Zum Schluss wird die Bedeutung der Gedächtnisseffekte für die Steuerung der dissipativen Dynamik diskutiert und die Theorie der Optimalen Kontrolle neu formuliert um eine zeitliche Nicht-Lokalität in der Bewegungsgleichung des Molekularsystems zu berücksichtigen.This work is dedicated to a further development of the density matrix theory and its application to the study of ultrafast laser pulse induced dynamics in molecular systems interacting with a thermal environment. Two topics are considered, first the so-called memory effects are analyzed which result from a reduced description of the molecular system excluding the environmental degrees of freedom. And secondly, the laser pulse control of dissipative molecular dynamics is examined. The theoretical description of open quantum systems results in a time non-local equation of motion so that the evolution of the molecular system depends on its past. In this work a numerical method to solve the time non-local equations of motion has been developed and tested for a minimal model of a polyatomic molecule subject to the dissipative influence of an environment. An analytical solution of the equation of motion for the special case of very long standing memory is also achieved. To identify signatures of such memory effects in general case we compare this analytical solution with numerical calculations involving memory and with approximative computations ignoring time non-locality. For the excitation by a laser pulse shorter than the duration of the memory the molecular systems exhibit noticeably different dynamics than for the absence of the memory. The effects become significantly more pronounced with decreasing laser pulse durations. The second part of the work concentrates on the application of the optimal control theory to guide molecular dynamics. Optimal control theory provides laser pulses which are designed in such a manner to fulfill certain control tasks, e.g. the population of a desired vibrational level of the molecular system or the placement of a wavepacket on a prescribed position on the molecular potential energy surface. As a first example the control of the dissipative photo-induced electron transfer in a donor--bridge--acceptor systems has been particularly considered ignoring the memory. The controllability of the electron transfer has been discussed and the mechanism by which it becomes possible has been identified. We have found the control of electron transfer reactions feasible even under the influence of dissipation although the yield of the control decreases drastically with increasing dissipation. In the presence of dissipation mechanism of the control has been found to change. The feasibility of the reproduction of the control pulses resulting for the optimal control theory in the experiment has been discussed and methods have been presented how to check the efficiency of the reproduction of optimal control pulses by liquid crystal pulse shapers, prevailingly used in modern control experiments. To distinguish different control tasks a quantitative measure has been introduced characterizing complexity of the control task. The optimal control theory has also been formulated for molecular systems showing static disorder and applied on an ensemble of molecules exhibiting random orientations. Finally, the importance of memory effects for the control of dissipative dynamics has been discussed and the optimal control theory has been formulated to account for a time non-locality in the equation of motion for molecular systems.
31
Price, Jonathan Hugh Vaughan. „The development of high power, pulsed fiber laser systems and their applications“. Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15475/.
Annotation:
Rare-earth doped silica fibers have been used for many years to create continuous-wave lasers, and Er-doped fiber amplifiers are now widely used in telecommunications. In addition, cladding pumped fiber allows the efficient conversion of multimode radiation from high power, low cost, broad-stripe semiconductor laser diodes into the single-mode emission of fiber lasers. With its broad gain bandwidth and high optical conversion efficiency, Yb-doped silica fiber represents an attractive medium for the generation and amplification of high energy ultrashort optical pulses. However, these potential advantages of Yb-doped silica fiber as a gain and nonlinear medium for mode-locked lasers and ultrashort pulse amplifiers have been less well studied, and it was not until 1999 that significant research interest first appeared in Yb-fiber chirp pulse amplifier (CPA) systems. This thesis describes the development of the first practical and stable, femtosecond, Yb-fiber oscillator, and of an Yb-fiber amplifier based CPA system (pulses ~10 μJ, <500 fs). Novel aspects of the system include the use of a high extinction ratio Electro-Optic modulator for pulse selection, and the development of a compact chirped-fiber-Bragg-grating (CFBG) pulse stretcher that provides both 2nd and 3rd order chirp compensation. Recently published theoretical results have demonstrated that the asymptotic solution for ultrashort pulses in a high gain fiber amplifier is a linearly chirped pulse, which can therefore be recompressed with a standard grating compressor. This thesis reports the first experimental comparison of nonlinear pulse evolution towards the asymptotic form using a cascaded amplifier system. The "direct amplification" system was constructed by removing the CPA stretcher grating, which also enabled the use of a less dispersive and more compact compressor. Further system development should lead to the generation of ultrashort pulses at high average power levels and >100 kHz repetition rates. Holey fiber (HF) is a recently developed technology that uses rings of air holes around a solid core to confine the optical field by average-index effects. Fibers are highly suitable for applications using nonlinear optics because of the tightly confined mode and long interaction lengths. The increased mode confinement possible using HF means that small-core, high air-fill fraction HF are an attractive nonlinear medium. Furthermore, the high index contrast in such fibers can create a strong (anomalous) waveguide contribution to the dispersion, and such HFs can have anomalous dispersion at wavelengths <1.3 μm, where conventional fiber has normal dispersion. Therefore HFs can support solitons in new wavelength bands. This thesis reports the first demonstration of linear dispersion compensation, soliton transmission, and visible continuum generation seeded by a 1.06 μm Yb-fiber source. In addition, an experimental study is reported that used HF seeded from a Ti:Sapphire laser to generate continuum in distinct transverse spatial modes of a HF. Numerical simulations suggested that the observed enhancement in UV generation from a higher order mode could be due to differences in the dispersion profiles of the fundamental and higher order transverse modes. Finally, the development of a novel source of <200 fs pulses, continuously tuneable in wavelength from 1.06-1.33 μm, based on the soliton self-frequency-shift principle, is described. The source was constructed from a diode-pumped Yb-doped HF amplifier, and the Yb-fiber oscillator described above. The diode pump power controlled the output wavelength.
32
Piper, Andy. „The development of high power, pulsed fiber laser systems and their applications“. Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/42427/.
Annotation:
Due to the recent renewal in interest in fiber laser technology, continuous wave (c.w.) laser technology using rare-earth doped silica fibers has developed rapidly in the past few years. In the late 80s, Erbium Doped Fiber Amplifiers were commercialised and became widely used in the telecommunications industry. Yb-doped silica fiber is particularly attractive as its broad gain bandwidth and high optical efficiency make it a preferred choice for both pulsed and c.w. high power fiber laser and amplifier applications. With the advent of cladding pump technology, low cost, high power broad-stripe semiconductor laser diodes with multimoded radiation could be efficiently used to produce high power Yb-doped silica fiber lasers with either single (~ 1 kW) or multimode (~ 10 kW) emission. Finally, the development and demonstration of a novel gain switched laser diode operating at 1 µm is reported. Using this gain switched laser diode as a seed source; the output gain switched pulses were compressed to 20 ps using a fiber compressor and thereafter amplified to achieve an output average power of 11.1 W at 1 GHz repetition rate using an YDFA cascade. Additional novel work was carried out later where a linearly dispersive CFBG was used to compress the pulses to 16.6 ps. These pulses were later amplified to average powers of 321 W at 1 GHz. This we believe is the highest output power ever achieved for a short pulse fiber laser system.
33
Yilmaz, Remziye Pinar. „Timing Issues In A Terawatt Laser System“. Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610017/index.pdf.
Annotation:
In the laser market, there have been various kinds of lasers designed and utilized for
different purposes. As time goes on, their powers have been gradually increased
from kilowatts (kW) to terawatts (TW). One of the most famous methods in laser
science technology is Chirped Pulse Amplification (CPA) which enables table-top
terawatt laser systems. This method provides high output power (tens of TW), very
short pulse duration (few tens of femtoseconds) and large energy (mJ) for ultrafast
lasers. One of the most well-known ultrafast lasers is Titanium:Sapphire laser. This
thesis work concentrates on how delay a pulse generator should work so that Verdi
and the oscillator pulse coincide. Moreover, by assembling a terawatt laser system,
the most important issues are timing between seed pulse and pump pulse and time
delays of all components of this systemautocorrelator, pump source, photodiode, Pockels cell, stretcher and dazzler were examined. This timing and the time delays were separately identified for terawatt laser systems. In this study, the aim is to attain the terawatt level output by arranging pump and seed pulses timing and the time delay on the components of the laser system setup.
34
Adamonis, Jonas. „High power Nd:YAG laser for pumping of OPCPA systems“. Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093516-33211.
Annotation:
This thesis was aimed to develop, investigate and optimize high power Nd:YAG laser system for OPCPA (Optical Parametric Chirped Pulse Amplifiers) pump. The particular attention is paid for the temporal characteristics of the Nd:YAG amplifies output pulse. Employment of Fabry-Perоt etalons in the cavities of two-stage Nd:YAG regenerative amplifier enables for amplified pulse stretching from 60 fs to ~ 100 ps pulse widths. The modulation of amplified pulse envelope is minimal when ration of thickness of the etalons is around 2. Envelope modulation can be controlled by changing the reflectivity of etalons. In order to improve amplified pulse contrast, we for the first time to our knowledge implemented second order intensity dependent filter, based on the effect of fundamental pulse polarization rotation in unbalanced second harmonic generators. By using this method, the contrast of the output pulses was improved by >102 times. We also demonstrated that Gaussian pulses from the output of Nd: YAG amplifiers can be transformed into flat–top pulses by using cascade second harmonic generation processes. The developed high output energy Nd:YAG amplifiers system for OPCPA pumping is optically synchronized with pulses of Yb:KGW oscillator and features two 532 nm outputs with pulse parameters: a) Gaussian pulse profile, ~ 300 mJ energy, 75 ps pulsewidth; b) hiper- Gaussian pulse profile, ~100 mJ energy, pulse width 100-150 ps.Disertacija yra skirta sukurti, ištirti ir optimizuoti didelės galios Nd: YAG lazerių sistemą efektyviam moduliuotos fazės signalų optinių parametrinių stiprintuvų kaupinimui. Ypatingas dėmesys yra skiriamas Nd:YAG stiprintuvų išvadinių impulsų laikinių parametrų formavimui. Pademonstravome, kad Fabry-Pero interferometrų panaudojimas Nd:YAG dvipakopio regeneracinio stiprintuvo rezonatoriuose leidžia stiprinamų impulsų trukmę padidinti nuo ~ 60 fs iki 100 ps. Tuo tarpu išvadinių impulsų laikinės plėtros mastas bei gaubtinės moduliacijos gylis gali būti valdomas keičiant etalonų atspindžio koeficientą, o jų gaubtinės moduliacijos vertė mažiausia, kai etalonų storio santykis artimas 2. Sustiprintų impulsų kontrasto gerinimui pirmą kartą pritaikėme netiesinį antros eilės filtrą, veikiantį fundamentinės spinduliuotės poliarizacijos sukimo, išderintame antros harmonikos generatoriuje, efekto pagrindu. Tokiu būdu Nd:YAG stiprintuvuose sustiprintų impulsų kontrasto vertė pagerinta apie 102 kartų. Taip pat pademonstruota, kad Nd: YAG stiprinimo sistemos išėjime naudojant pakopinius antros harmonikos generacijos procesus, Gauso formos impulsus galima transformuoti į hipergauso impulsus. Sukurta didelės išvadinės energijos pikosekundinė Nd:YAG stiprintuvų sistema yra optiškai sinchronizuota su užduodančio femtosekundinio Yb:KGW osciliatoriaus impulsais ir turi ~ 300 mJ , 75 ps trukmės Gauso impulsų bei 100 mJ, > 100 ps trukmės hipergauso laikinės formos impulsų išvadus.
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Mason, Michael Brett. „A sub-50 fs titanium-sapphire chirped pulse amplification laser system“. Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326264.
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Haram, Nida. „Reaction microscope studies of relativistic strong-field effects in atomic systems“. Thesis, Griffith University, 2020. http://hdl.handle.net/10072/391063.
Annotation:
The ultrashort pulsed laser sources and reaction microscope have been extensively employed to explore the fundamental strong-field ionisation mechanisms over the last three decades. The aim of this thesis is to gain insight into the subtleties of the photoelectron dynamics influenced by the few-cycle laser pulses. In particular, it addresses the possible factors that may affect the photoelectron dynamics. However, these factors are typically ignored under the umbrella of some commonly used approximations, which include the effect of magnetic field component of the laser field and attractive Coulomb field of the parent ion on the photoelectron dynamics. These effects, collectively called relativistic nondipole effects, are known to have subtle influence on the recollision electron dynamics and may ultimately affect the important strong-field processes relying on the recolliding photoelectrons. In this thesis, we explore the relativistic nondipole effects by performing strong-field ionisation experiments on the noble gas atoms using linearly-polarised near-infrared few-cycle laser pulses. The high-resolution photoelectron momentum spectra are acquired using a reaction microscope, since these effects often manifest themselves in the transverse electron momentum distribution (TEMD).
The first study is undertaken at different intensities in the range 1014–1015 W/cm2 using Ar as the target gas to investigate the dependence of these nondipole effects on the intensity. The peak of the TEMD is found to be shifted in the direction opposite to the laser propagation (counter-intuitive) direction with increasing laser intensity. The combined effect of the magnetic field induced drift and Coulomb focusing of the parent ion accounts for this counter-intuitive peak shift of the TEMD. Owing to the importance of these effects in the strong-field ionisation processes, an ab initio fully relativistic 3D model based on the time-dependent Dirac equation (3D-TDDE) is formulated by our theoretical collaborator Igor Ivanov. The theoretical predictions agree quite well with the experimental results over the entire intensity range. Moreover, the simulations based on a Yukawa potential further support the interpretation, which suggests that the Coulomb force is responsible for the counter-intuitive peak shift, since they do not reveal any peak shift.
The second study reports on the energy-resolved relativistic nondipole effects, with the experiments performed at 1.5×1015 W/cm2 using Ar and Ne as target gases revealing unique low-energy features in the photoelectron momentum spectra. The experimental and theoretical results show energy-dependent tilting of the TEMD and spectral narrowing for the low-energy photoelectrons. The peak shift of the TEMD for the low-energy photoelectrons is found to be in the counter-intuitive direction, whereas high-energy photoelectrons always exhibit a positive peak shift. To get an intuitive picture of the underlying physical mechanisms, a modified three step model is proposed.
In short, the results of this work need to be taken into account for the most commonly used laser parameters to explain the processes relying on recollision. Also, the theoretical model based on 3D-TDDE is essential to describe the strong-field ionisation processes at the truly relativistic intensities i.e. > 1018 W/cm2.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Blanquer, Eric. „LADAR Proximity Fuze - System Study -“. Thesis, KTH, Reglerteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-106247.
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LADAR (Laser Detection and Ranging) systems constitue a direct extension of the conventional radar techniques. Because they operate at much shorter wavelengths, LADARs have the unique capability to generate 3D images of objects. These laser systems have many applications in both the civilian and the defence fields concerning target detection and identification. The extraction of these features depends on the processing algorithms, target properties and 3D images quality. In order to support future LADAR hardware device developments and system engineering studies, it is necessary to understand the influences of the phenomena leading to the final image. Hence, the modelling of the laser pulse, propagations effects, reflection properties, detection technique and receiver signal processinghave to be taken into account. A complete simulator has been developed consisting of a graphical user interface and a simulation program. The computer simulation produces simulated 3D images for a direct detection pulse LADAR under a wide variety of conditions. Each stage from the laser source to the 3D image generation has been modelled. It yields an efficient simulation tool which will be of help in the design of the future LADAR systems and gauge their performances. This master’s thesis contains the theoretical background about laser used to build the simulation program. The latter is described schematically in order to provide an insight for the reader. The graphical interface is then presented as a short user’s manual. Finally, in order to illustrate the possibilities of the simulator, a collection of selected simulations concludes the report.
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Phillips, Andrew Julian. „Optically amplified digital pulse position modulation systems“. Thesis, Manchester Metropolitan University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260069.
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Chen, Junewen. „Development and applications of a high intensity ultrashort pulse UV laser system“. Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46710.
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Butt, Nathaniel J. „Development and Thermal Management of a Dynamically Efficient, Transient High Energy Pulse System Model“. Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527602141695356.
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Camacho, Garibay Abraham. „Dynamics of Highly Charged Finite Systems Induced by Intense X-ray Pulses“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-212203.
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The recent availability of X-ray Free Electron Lasers (XFELs) has opened a completely new and unexplored regime for the study of light-matter interactions. The extremely bright intensities delivered by XFELs can couple many photons into the target, turning well known interactions such as photoionization and scattering into new, non-linear, complex many-body phenomena. This thesis reports theoretical investigations aiming to improve the understanding of the fundamental processes and dynamics triggered by intense X-ray pulses, with a special focus in finite systems such as molecules and clusters.
Sequential multiple photoionization in atomic clusters was investigated, where previous observations were extended for higher charge states where direct photoionization is frustrated. Through a rate equation study and subsequent molecular dynamics simulations, it was found that frustrated ionization is partially responsible for the low-energy peak observed in the electron energy spectrum. The influence of plasma evaporation over the formation of the sequential low-energy peak was also investigated, identifying the effects of the system size and photon energy.
Multiple channel ionization was also investigated for the case of fullerenes. This is done through a series of studies, starting from a simplified rate equation scheme, and culminating with full molecular dynamics simulations. From these results, a good insight was obtained over the origin, physical meaning, and relevant parameters that give rise to the complicated features observed in the electronic spectra. The mechanisms responsible of all these features are expected to be present in other systems, making these results quite general.
Diffractive imaging of biomolecules was studied in a final step, with a particular focus on the influence of intramolecular charge transfer mechanisms. To this end a conformer of T4 Lysozyme was used, a representative enzyme with well known structure. Charge migration is found to allow for additional processes such as proton ejection, a mechanism which enables an efficient release of energy from the system. This mechanism considerably suppresses structural damage for heavy ions, improving the quality of the measured diffraction patterns.
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Yang, Chang. „Ultra-Compact Grating-Based Monolithic Optical Pulse Compressor for Laser Amplifier Systems“. Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/731.
Annotation:
Ultra-short and high-peak-power laser pulses have important industrial and scientific applications. While direct laser amplification can lead to peak powers of several million watts, higher values than these cannot be achieved without causing damage to the amplifier material. Chirped pulse amplification technique is thus invented to break this barrier. By temporally stretching pulses before entering amplifier, the pulse peak power is significantly reduced and thus becomes safe to be passed through the amplifier. After amplification, a compressor is used to recover the pulse width, and high-power ultra-short laser pulses are produced. Chirped pulse amplification technology increases the pulse energy by transferring the damaging effects of high-peak power laser pulses from the vulnerable amplifier to a relatively robust compressor system. The compressor is therefore a crucial device for producing high peak powers. However, there are some major drawbacks associated with it. First, compressors in high-energy laser system are usually over 1 cubic meter in size. For many applications, this large and cumbersome size is a limiting factor. Second, compressors are sensitive to outside disturbances; a little misalignment can lead to failure of pulse compression process. Third, gratings with large uniformly ruled area are difficult to fabricate, which impose a limit on achievable peak powers and pulse durations of laser pulses through the use of conventional compressors. In this project, we present a grating-based monolithic optical compressor that offers a way around some of the major problems of existing compressors. By integrating the key optical components, one can make a robust and monolithic compressor that requires no alignment. In the new scheme, folding the optical path with reflective coatings allows one to design a compressor of significantly reduced size by minimizing both the longitudinal and transverse dimensions of the device. The configuration and operation mechanism of this novel compressor are described. A method for calculating the volume of the compressor is investigated. This is validated by computing the size of a specific monolithic compressor. Simulation results obtained through finite-difference time-domain method are presented, proving that the new compressor provides a compact, portable, and robust means for temporally compressing long duration pulses.
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Stehmann, Timo. „Development and optimisation of a solid-state pulsed power supply for a CO₂ TEA laser“. Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53359.
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Thesis (MSc)--Stellenbosch University, 2003.ENGLISH ABSTRACT: With technological advances in solid-state switches the modernization of conventional pulsed power supplies utilizing thyratrons has become possible. A novel pulsed power supply is designed where two series-stacked IGBTs (rated at 1700 V and 300 A each) are used to replace a thryatrondriven pulsed power supply for a mini CO2 TEA laser. The mini CO2 TEA laser is firstly characterized in order to optimize the design of the pulsed power supply. It is found that stable laser discharges can be obtained with electrode voltage rise-times of 150 ns or less. Furthermore, the optical output energy and the efficiency of the laser have been significantly increased by reducing the peaking capacitor size of the pulsed power supply. The two stacked IGBTs switch a C-C transfer loop and the generated pulse is stepped up by a pulse transformer and is compressed by a two-stage magnetic pulse compression unit. Theoretically and through measurements it is shown that automatic voltage sharing between the two IGBTs can be obtained if the turn-on time of the IGBTs is much faster than the transfer time of the switched C-C transfer loop. Lifetime tests reveal that high-power IGBTs are able to reliably switch pulses with peak currents between 4 and 5 times the rated average current of the device. Under laser fault conditions, i.e. laser arcing or missing laser discharges, the reliability of the pulser can be increased by using over-voltage snubbers. In addition, it was found that the internal diode of IGBT modules can eventually fail under the prevalence of laser fault conditions. A modular construction approach is used where components of the pulsed power supply are preassembled. A new rectangular layout of the magnetic pulse compression unit is utilized in order to minimize size and simplify the final construction and assembly.
AFRIKAANSE OPSOMMING: Nuwe ontwikkeling in vastetoestand-skakelaars het die modernisering van laser-pulskragbronne moontlik gemaak. ’n Nuwe kragbron wat gebruik maak van twee seriegeskakelde IGBT’s is ontwerp om ’n Tiratron-gedrewe laserkragbron te vervang, wat vir ’n mini-C02-TEA-laser gebruik word. Die laser is vooraf eers gekarakteriseer om sodoende die laserkragbron te optimeer. Daar is bevind dat stabiele laserontladings verkry kan word met spanningstygtye van 150 ns of minder. Verder kan die uittree-energie van die laser beduidend verhoog word deur die uittreekapasitore (eng.: peaking capacitors) van die laserkragbron te verminder. Die twee serie-geskakelde IGBT’s skakel ’n C-C oordraglus. Die spanning van die gegenereerde puls word deur ’n pulstransformator verhoog en die stygtyd van die puls word met ’n twee-stadium magnetiese pulskompressor verlaag. Teoreties en deur metings kan getoon word dat eweredige spanningsverdeling tussen die twee IGBT’s outomaties verkry kan word indien die skakeltye van die IGBT’s baie vinniger as die oordragstyd van die C-C oordraglus is. Toetse het getoon dat IGBT’s pulse met piekstrome van tussen vier tot vyf keer die gespesifiseerde gemiddelde stroom betroubaar kan skakel. Tydens laserfouttoestande kan die betroubaarheid van die IGBT verhoog word deur oorspanningsgapsers te gebruik, maar onder fouttoestande wat voortduur, kan die IGBT se interne diode vemietig word. Die komponente van die laserkragbron is as modules vervaardig, wat op ’n maklike wyse gemonteer kan word. ’n Nuwe reghoekige uitleg is gebruik vir die konstruksie van die magnetiese pulskompressor, waarmee die grootte van die pulskompressor geminimeer en die konstruksie vergemaklik is.
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Loeser, Markus [Verfasser], Roland [Akademischer Betreuer] Sauerbrey, Ulrich [Gutachter] Schramm und Peter [Gutachter] Hartmann. „Diode-Pumped High-Energy Laser Amplifiers for Ultrashort Laser Pulses : The PENELOPE Laser System / Markus Loeser ; Gutachter: Ulrich Schramm, Peter Hartmann ; Betreuer: Roland Sauerbrey“. Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://d-nb.info/1151816930/34.
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Singh, Pooja. „Quantum Coherent Control and Propagation in Lambda System“. Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849750/.
Annotation:
Strong coherence in quasi-resonant laser driven system interferes with effective relaxations, resulting in behaviors like, coherent population trapping and Electromagnetically induced transparency. The Raman system can optimize this utilizing excited coherence in the lambda system when exposed to counter- intuitive pump-stokes pulses. The phenomenon can result in complete population transfer between vibrational levels called Stimulated Raman adiabatic passage(STIRAP). STIRAP and CHIRAP have been studied with Gaussian and chirped pulses. The optical propagation effects in dense medium for these phenomenon is studied to calculate the limitations and induced coherences. Further, the effect of rotational levels has been investigated. The molecular vibrational coherence strongly depends on the effect of rotational levels. The change in coherence interaction for ro-vibrational levels are reported and explained. We have considered the effects on the phase of radiation related to rotational mechanical motion of quantum system by taking advantages in ultra strong dispersion medium provided by quantum coherence in lambda system. The enhanced Fizeau effect on a single atom is observed.
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Doñate, Buendía Carlos. „Synthesis of nanomaterials by high throughput pulsed-laser based systems: Application in biomedicine and material processing“. Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/668339.
Annotation:
The work developed in this thesis is based on the study of systems for the generation of nanoparticles in liquids by means of pulsed lasers, improving their production and using the generated nanoparticles in applications of great technological relevance such as biomedical imaging or additive manufacturing. For the femtosecond laser production improvement, the novel implementation of a spatio temporal focusing system is proposed which, by varying the temporal pulse duration out-of-focus, suppresses nonlinear effects in the liquid medium and the associated energy losses. For the colloidal size reduction by fragmentation, a continuous flow system is proposed that allows to increase the control over the irradiation parameters while ensuring homogeneous irradiation. Finally, the carbon quantum dots generated are used as fluorescent markers and different metal and oxide nanoparticles are synthesized for their later application as bactericides and in the improvement of materials used in additive manufacturing.El trabajo desarrollado en esta tesis se basa en el estudio de sistemas de generación de nanopartículas en líquidos mediante láser pulsado, mejorando su producción y empleando los nanomateriales generados en aplicaciones como imagen biomédica o additive manufacturing. Para la mejora en la producción mediante láser de femtosegundo se propone la implementación de un sistema de focalización espacio-temporal que, mediante la variación de la duración temporal de los pulsos fuera de foco, consigue suprimir los efectos no lineales en el medio líquido. Para la mejora en el proceso de reducción del tamaño de coloides, se propone un sistema de flujo continuo que aumenta el control sobre los parámetros de irradiación. Finalmente, los puntos cuánticos de carbono generados se utilizan como marcadores fluorescentes y se sintetizan distintas nanopartículas metálicas y óxidos para su posterior aplicación como bactericidas y en la mejora de materiales utilizados en fabricación aditiva.
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Gross, Michael Charles. „High-rate, short-pulse sources:jitter and pedestal level in optical time-division multiplexing“. Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5405.
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Gross, Michael Charles. „High-rate, short-pulse sources jitter and pedestal level in optical time-division multiplexing /“. Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180157/unrestricted/gross%5Fmichael%5Fc%5F200312%5Fphd.pdf.
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Efimov, Anatoly. „Adaptive control of lasers and their interactions with matter using femtosecond pulse shaping“. [Florida] : State University System of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/ane5949/thesis.pdf.
Annotation:
Thesis (Ph. D.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains v, 181 p.; also contains graphics. Vita. Includes bibliographical references (p. 165-180).
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Driever, Steffen. „Development of an ytterbium fibre based chirped pulse amplification laser system for high harmonic generation“. Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/26273.
Annotation:
In this thesis, I describe the development of a high repetition rate femtosecond fibre based chirped pulse amplification system (FCPA) for strong-field physics experiments. This project was set in a newly established sub-group of the Laser Consortium at Imperial College London with the aim to push the strong-field and attosecond science experiments to be conducted at 100s of kHz repetition rate. It was important to design and implement a compact, CEP stable, high repetition rate fibre CPA system. Custom optics and mounts were employed in order to achieve a compact stretcher and compressor design. The stretcher was designed to stretch the oscillator pulses with a bandwidth of 14nm and a duration of 90 fs to 1 ns to avoid non-linearities in the fibre amplifier. It is based on an Offner type configuration. The fast rise time RTP based Pockels cell can be adjusted to deliver 50 -350 kHz of repetition rate to the large mode area (LMA) ytterbium doped fibre with 30 um core and 250 um cladding (Yb1200-30/250DC-PM, Nlight). It was possible to generate up to 13 uJ of pulse energy at 100 kHz repetition rate before compression with 14W pump power. Higher pulse energies up to 130 uJ have been demonstrated at 38W of pumping (55W pump diode Nlight), however mechanical instabilities impaired the spectral and spatial performance at this power level. Improvements to optimise the performance of the system are suggested in the conclusion. Additionally to this experiments in the near-IR have been conducted on post compression mechanisms. The principle of filamentation was employed to generate tunable few-cycle pulses at wavelengths from 1.6 - 2 um and subsequent high harmonic generation in a proof of principle experiment. These results were published in Applied Physics Letters [1] and Journal of Physics B: At. Mol. Opt. Phys. [2].