The goal of this thesis is developing a two-color Ytterbium (Yb) fiber amplifier system that can be used for generation of mid-infrared radiation. Previously, our group reported generating 20 µW of average power, at a wavelength of 18µm. This was accomplished through the amplification of a two color-seed with peaks at 1040nm and 1110nm, through a two stage amplification without any compression. The mid-infrared radiation (MIR) was generated with a 4.5 ps pulse duration by the method of difference-frequency mixing, using 300 mW of average power from the two-color Yb-fiber amplifier. Because there was no limitation by two-photon absorption, MIR output power could be scaled by increasing the amplifier power. The current project aims to increase the peak power of the laser pulses to improve the efficiency of the nonlinear mixing. The two-colour seed is generated by continuum generation in a photonic crystal fibre, pumped by 200 mW of average power from a mode-locked Yb:fibre laser. In order to efficiently increase the energy of the two wavelengths, the 4.6 mW seed pulse is now pre-amplified up to 21 mW in a 2.7 m length single mode, single core Yb:fibre . The pre-amplifier used a double-ended pumping scheme with two single mode diode lasers at 976 nm each having 150 mW maximum pump power. A notch filter was placed in the output beam to eliminate any Amplified Spontaneous Emission. After further amplification in a 7 m length of double clad, Yb-fibre, a maximum average power of 727 mW was achieved for two colours peaked at 1035 nm and 1105 nm wavelengths. The pump power for this stage was 6 W. A grating stretcher is now used to select the two-colour input along with stretching the pulses. A three grating compressor is used to compress the output pulses to 466 fs pulse duration. After compression the average power of the two colours is 350 and 110 mW for wavelengths at 1035 and 1105nm, respectively. These higher power pulses are planned to be used to increase the mid-infrared generation efficiency.

The goal of this thesis is developing a two-color Ytterbium (Yb) fiber amplifier system that can be used for generation of mid-infrared radiation. Previously, our group reported generating 20 µW of average power, at a wavelength of 18µm. This was accomplished through the amplification of a two color-seed with peaks at 1040nm and 1110nm, through a two stage amplification without any compression. The mid-infrared radiation (MIR) was generated with a 4.5 ps pulse duration by the method of difference-frequency mixing, using 300 mW of average power from the two-color Yb-fiber amplifier. Because there was no limitation by two-photon absorption, MIR output power could be scaled by increasing the amplifier power. The current project aims to increase the peak power of the laser pulses to improve the efficiency of the nonlinear mixing. The two-colour seed is generated by continuum generation in a photonic crystal fibre, pumped by 200 mW of average power from a mode-locked Yb:fibre laser. In order to efficiently increase the energy of the two wavelengths, the 4.6 mW seed pulse is now pre-amplified up to 21 mW in a 2.7 m length single mode, single core Yb:fibre . The pre-amplifier used a double-ended pumping scheme with two single mode diode lasers at 976 nm each having 150 mW maximum pump power. A notch filter was placed in the output beam to eliminate any Amplified Spontaneous Emission. After further amplification in a 7 m length of double clad, Yb-fibre, a maximum average power of 727 mW was achieved for two colours peaked at 1035 nm and 1105 nm wavelengths. The pump power for this stage was 6 W. A grating stretcher is now used to select the two-colour input along with stretching the pulses. A three grating compressor is used to compress the output pulses to 466 fs pulse duration. After compression the average power of the two colours is 350 and 110 mW for wavelengths at 1035 and 1105nm, respectively. These higher power pulses are planned to be used to increase the mid-infrared generation efficiency.

In some high-field laser-plasma experiments, it is advantageous to accompany the main high-energy (~1 J) laser with a second high-energy pulse (~0.1 J) which has been frequency-shifted by ~10-20%. Such a pulse-pair would have a low walk-off velocity while remaining spectrally distinct for use in two-color pump-probe experiments. Moreover, by shifting the second pulse by ~plasma frequency, it is theoretically possible to exercise some amount of control over a variety of laser-plasma instabilities, including forward Raman scattering, electromagnetic cascading, and relativistic self-focusing. Alternatively, the two pulses may be counter-propagated so that the collide in the plasma and create a slowly-propagating beatwave which can be used to inject electrons into a laser wakefield accelerator. The design, characeterization, and performance of a hybrid chirped-pulse Raman amplifier (CPRA)/Ti-Sapphire amplifier are reported and discussed. This hybrid system allows for the generation of a high-energy (>200 mJ), broadband (15-20 nm bandwidth FWHM), short duration (>100 fs duration) laser sideband. When amplified and compressed, the Raman beam's power exceeds 1 TW. This sideband is combined with the primary laser system to create a bi-color terawatt laser system which is capable of performing two-color high-field experiments. This two-color capability can be added to any commercial terawatt laser system without compromising the energy, duration or beam quality of the primary system. Preliminary two-color laser-plasma experiments are also discussed. / text

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 system / autocorrelator, 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.

Rapidly developing areas of high field physics, generation of high order harmonics or isolated attosecond pulses, require high peak power few-cycle pulse sources. Optical parametric chirped pulse amplification (OPCPA) has shown potential to satisfy these requirements and at present OPCPA is the leading technology for high energy few-cycle pulse table-top systems. The main objectives of this thesis were to investigate optical parametric amplification of broadband seed pulses in femtosecond and picosecond regimes, to develop and optimize a compact TW-scale OPCPA system intended for various applications in areas of high-field physics. In this thesis the main concept of such system is discussed, advantages and disadvantages of proposed approach are analyzed, the setup is compared to other world known systems. In this thesis an original approach for power scaling of regenerative amplifier by implementing several active elements in prolonged resonator has been proposed and investigated. Femtosecond pulse amplification in dual active element Yb:KGW regenerative amplifier has been demonstrated, resulting in boost of average output power to 30 W. Broad bandwidth pulse generation, parametric amplification and compression to transform limited values were analyzed both numerically and experimentally. White light continuum generation in bulk material for broadband seed formation, its further optical parametric amplification in noncollinear scheme were investigated and Yb:KGW driven... [to full text] / Stiprių laukų fizikos srities tyrimams, aukštų eilių harmonikų ir pavienių atosekundinių impulsų generavimui, yra reikalingos kompaktiškos teravatų smailinės galios kelių optinių ciklų išvadinių impulsų lazerinės sistemos. Optinis parametrinis „čirpuotų“ impulsų stiprinimas yra vienas pagrindinių metodų leidžiančiu pasiekti šiems taikymams reikalingus lazerinių sistemų parametrus. Šios disertacijos darbo tikslas – ištirti femtosekundinės ir pikosekundinės trukmės impulsų stiprinimą optiniuose parametriniuose stiprintuvuose užkratui naudojant ypač plataus spektro signalą, bei sukurti ir optimizuoti čirpuotų impulsų parametrinio stiprinimo sistemą, užtikrinančią patikimą teravatų smailinės galios impulsų formavimą. Disertacijoje aptariama bendra tokios sistemos architektūra, nagrinėjami privalumai ir trūkumai, palyginama su kitomis pasaulyje egzistuojančiomis sistemomis. Šiame darbe pasiūlytas ir ištirtas lazerių vidutinės išvadinės galios didinimo metodas, naudojant kelis aktyviuosius elementus viename rezonatoriuje, ir pademonstruotas femtosekundinių impulsų stiprinimas šio metodo pagrindu sukonstruotame dviejų Yb:KGW aktyvių elementų regeneratyviniame stiprintuve, tokiu būdu padidinant lazerio išvadinę galią iki 30 W. Darbo metu sukonstruota bei ištirta Yb:KGW femtosekundiniu lazeriu kaupinamos baltos šviesos kontinuumo generavimo ir nekolinearaus kaupinimo optinio parametrinio stiprinimo sistema, kurios išvadinių impulsų energiją siekia 20 mikrodžiaulių, o impulsai... [toliau žr. visą tekstą]

Laser high-order harmonic generation in the presence of relatively weak interfering light is investigated. The interfering pulses intersect the primary harmonic-generating laser pulse at the laser focus. The interfering light creates a standing intensity and phase modulation on the field, which disrupts microscopic phase matching and shuts down local high harmonic production. Suppression of the 23rd harmonic (by two orders of magnitude) is observed when a counter-propagating interfering pulse of light is introduced. A sequence of counter-propagating pulses can be used to shut down harmonic production in out-of-phase zones of the generating volume to achieve quasi phase matching. Harmonic emission is enhanced in this case. A new high-power laser system with higher pulse energy has been constructed to further investigate quasi phase matching of high-order harmonics generated in difficult-to-ionize atomic gases (e.g., neon as opposed to argon). The new system can also be used to study harmonic generation in ions. A new counter-propagating beam produces a train of 5 pulses with regulated timing. In preliminary tests, the new system has produced high harmonics up to the 65th order in neon. This should increase with additional adjustments to the laser system. The high-order harmonics have also demonstrated to be useful for polarized reflectometry measurements of optical surfaces in the extreme ultraviolet (EUV) wavelength range.

High power thulium fiber lasers are useful for a number of applications in both continuous-wave and pulsed operating regimes. The use of thulium as a dopant has recently gained interest due to its large bandwidth, possibility of high efficiency, possibility of high power and long wavelength ~1.8 – 2.1 μm. The longer emission wavelength of Tm-doped fiber lasers compared to Yb- and/or Er-doped fiber lasers creates the possibility for higher peak power operation due to the larger nonlinear thresholds and reduced nonlinear phase accumulation. One primary interest in Tm-doped fiber lasers has been to scale to high average powers; however, the thermal and mechanical constraints of the fiber limit the average power out of a single-fiber aperture. One method to overcome the constraints of a single laser aperture is to spectrally combine the output from multiple lasers operating with different wavelengths into a single beam. In this thesis, results will be presented on the development of three polarized 100 W level laser systems that were wavelength stabilized for SBC. In addition to the development of the laser channels, the beams were combined using bandpass filters to achieve a single near diffraction-limited output. Concurrently, with the development of high average power systems there is an increasing interest in femotosecond pulse generation and amplification using Tm- doped fiber lasers. High peak power sources operating near 2 µm have the potential to be efficient pump sources to generate mid-infrared light through supercontinuum generation or optical parametric oscillators. This thesis focuses on the development of a laser system utilizing chirped pulse amplification (CPA) to achieve record level energies and peak powers for ultrashort pulses in Tm-doped fiber. iv A mode-locked oscillator was built to generate femtosecond pulses operating with pJ energy. Pulses generated in the mode-locked oscillator were limited to low energies and contained spectral modulation due to the mode-locking mechanism, therefore, a Raman-soliton self-frequency shift (Raman-SSFS) amplifier was built to amplify pulses, decrease the pulse duration, and spectrally clean pulses. These pulses were amplified using chirped pulse amplification (CPA) in which, limiting factors for amplification were examined and a high peak power system was built. The primary limiting factors of CPA in fibers include the nonlinear phase accumulation, primarily through self-phase modulation (SPM), and gain narrowing. Gain narrowing was examined by temporally stretching pulses in a highly nonlinear fiber that both stretched the pulse duration and broadened the spectrum. A high peak power CPA system amplified pulses to 1 µJ energy with 300 fs compressed pulses, corresponding to a peak power >3 MW. High peak power pulses were coupled into highly nonlinear fibers to generate supercontinuum

This thesis deals with the design of a stretcher and compressor systems used for the chirped pulse amplification method for the L4 beamline. The L4 beamline is being developed for the ELI Beamlines project and aims to deliver pulses with peak power of 10 petawatt, central wavelength of 1060 nanometers, pulse duration of 150 femtoseconds and energy of 1500 Joules. Since the laser induced damage threshold and aperture of commercial diffraction gratings is currently a limiting factor in reaching higher peak powers, it was necessary to increase the effective aperture of the compressor using either tiled grating or object-image-grating self tiling methods. These two methods are compared for two compressor configurations using either 1740 ln/mm or 1136 ln/mm diffraction gratings, methods for their alignment are discussed and the selected alignment method is experimentally tested. Moreover, an analytical theory connecting the Seidel aberrations of the stretcher imaging system with the spectral phase deviation of the stretched pulse is presented. This theory is applied to commonly used Banks and Offner stretcher designs and it is demonstrated how it can be employed for the suppression of residual spectral phase of compressed pulses. Next, the design of the stretcher for the L4 beamline based on this theory is...

La chaîne laser Apollon 10PW est un projet de grande envergure visant à fournir des impulsions de 10 PW et atteindre des intensités sur cibles de 10^22 W/cm^2. Dans l’état de l'art actuel, les lasers à dérive de fréquence (CPA) de haute intensité à base de cristaux titane saphir (Ti:Sa), sont limités à des puissances de crête de 1,3 PW pour des impulsions de 30-fs, en raison du rétrécissement spectral par gain dans les amplificateurs. Pour accéder au régime multipetawatt, le rétrécissement de gain doit être évité. Pour cela une technique alternative d’amplification appelée amplification paramétrique optique d'impulsions à dérive de fréquence (OPCPA) est utilisée. Elle offre la possibilité d’amplifier sur des très larges bandes spectrales de gain et d’accéder à des durées d'impulsion aussi courtes que 10 fs. Le laser Appolon 10 PW exploite une technologie hybride d’OPCPA et de Ti:Sa-CPA pour atteindre in fine des impulsions de 15 fs avec une énergie de 150 J. L’OPCPA est réalisé essentiellement sur les étages d'amplification de basse énergie et de très fort gain (ou le rétrécissement par le gain se fait le plus ressentir), ceci pour obtenir des impulsions de 100 mJ, 10 fs. Deux étages OPCPA sont préus ; le premier en régime picoseconde, le second en régime nanoseconde, et subséquemment on utilisera le Ti:Sa pour l'amplification de très haute énergie pour atteindre le régime multi-Joule.Les travaux de cette thèse porte sur le pilote OPCPA du laser Apollon-10 PW et se concentre sur le développement d’une source d’impulsions ultra-courtes avec un contraste élevé. Pour atteindre l’objectif final de 15 fs, 150 J, le pilote doit permettre l’obtention d’impulsions dont le spectre supporte des durées de 10 fs, ceci avec un contraste temporel d'au moins 10^10. Dans cette thèse nous nous intéressons à la mise en œuvre des premiers étages du pilote. Ce travail concerne les étages de compression, de nettoyage d’impulsions et d’amplification OPCPA en régime picoseconde. Ainsi, en partant d'une source commerciale Ti:Sa délivrant des impulsions de 25-fs avec un contraste de 10^8, nous réalisons tout d’abord un élargissement spectral par auto-modulation de phase et une amélioration du contraste par génération de polarisation croisée (XPW). Ensuite, nous nous intéressons aux différents étireurs ps possibles incluant un filtre dispersif programmable (dazzler) en vue d’injecter l’OPCPA picoseconde de manière optimale. La solution directe utilisant un bloc de verre BK7 a été retenue et son association avec un compresseur compact pour le diagnostique de la compressibilité a été étudiée. Enfin, l’amplificateur OPCPA ps a été mis en œuvre dans des configurations à simple et double étages. / The Apollon-10 PW laser chain is a large-scale project aimed at delivering 10 PW pulses to reach intensities of 10^22 W/cm^2. State of the art, high intensity lasers based solely on chirped pulse amplification (CPA) and titanium sapphire (Ti:Sa) crystals are limited to peak powers reaching 1.3 PW with 30-fs pulses as a result of gain narrowing in the amplifiers. To access the multipetawatt regime, gain narrowing can be suppressed with an alternative amplification technique called optical parametric chirped pulse amplification (OPCPA), offering a broader gain bandwidth and pulse durations as short as 10 fs. The Apollon-10 PW laser will exploit a hybrid OPCPA-Ti:Sa-CPA strategy to attain 10-PW pulses with 150 J and 15 fs. It will have two high-gain, low-energy amplification stages (10 fs ,100 mJ range) based on OPCPA in the picosecond and nanosecond timescale and afterwards, and will use Ti:Sa for power amplification to the 100-Joule level.Work in this thesis involves the progression of the development on the Apollon-10 PW front end and is focused on the development of a high contrast, ultrashort seed source supporting 10-fs pulses, stretching these pulses prior to OPCPA and the implementation of the picosecond OPCPA stage with a target of achieving 10-mJ pulses and maintaining its bandwidth. To achieve the final goal of 15-fs, 150-J pulses, the seed source must have a bandwidth supporting 10-fs and a temporal contrast of at least 10^10. Thus from an initial commercial Ti:Sa source delivering 25-fs pulses with a contrast of 10^8, spectral broadening via self-phase modulation and contrast enhancement with cross polarized (XPW) generation was performed. Subsequently, the seed pulses were stretched to a few picoseconds to match the pump for picosecond OPCPA. Strecher designs using an acousto-optic programmable dispersive filter (dazzler) for phase control in this purpose are studied. A compact and straightforward compressor using BK7 glass is used and an associated compressor for pulse monitoring was also studied. Lastly, the picosecond OPCPA stage was implemented in single and dual stage configurations.

The Apollon-10 PW laser chain is a large-scale project aimed at delivering 10 PW pulses to reach intensities of 10^22 W/cm^2. State of the art, high intensity lasers based solely on chirped pulse amplification (CPA) and titanium sapphire (Ti:Sa) crystals are limited to peak powers reaching 1.3 PW with 30-fs pulses as a result of gain narrowing in the amplifiers. To access the multipetawatt regime, gain narrowing can be suppressed with an alternative amplification technique called optical parametric chirped pulse amplification (OPCPA), offering a broader gain bandwidth and pulse durations as short as 10 fs. The Apollon-10 PW laser will exploit a hybrid OPCPA-Ti:Sa-CPA strategy to attain 10-PW pulses with 150 J and 15 fs. It will have two high-gain, low-energy amplification stages (10 fs ,100 mJ range) based on OPCPA in the picosecond and nanosecond timescale and afterwards, and will use Ti:Sa for power amplification to the 100-Joule level.Work in this thesis involves the progression of the development on the Apollon-10 PW front end and is focused on the development of a high contrast, ultrashort seed source supporting 10-fs pulses, stretching these pulses prior to OPCPA and the implementation of the picosecond OPCPA stage with a target of achieving 10-mJ pulses and maintaining its bandwidth. To achieve the final goal of 15-fs, 150-J pulses, the seed source must have a bandwidth supporting 10-fs and a temporal contrast of at least 10^10. Thus from an initial commercial Ti:Sa source delivering 25-fs pulses with a contrast of 10^8, spectral broadening via self-phase modulation and contrast enhancement with cross polarized (XPW) generation was performed. Subsequently, the seed pulses were stretched to a few picoseconds to match the pump for picosecond OPCPA. Strecher designs using an acousto-optic programmable dispersive filter (dazzler) for phase control in this purpose are studied. A compact and straightforward compressor using BK7 glass is used and an associated compressor for pulse monitoring was also studied. Lastly, the picosecond OPCPA stage was implemented in single and dual stage configurations.