fast, powerful and efficientfemtocryble

vulgarisation pour le projet ANR femtocrybleWhat are 'New Yb-doped crystals and laser architectures for the development of a chain femtosecond laser high power' (FEMTOCRYBLE)'s three major research objectives? The main objective of FEMTOCRYBLE is to use newly developed Ytterbium (Yb)-doped lasers to improve the performance of diode-pumped femtosecond solid-state lasers in terms of power, pulse duration, energy and efficiency. For this, the first research objective concerns crystal improvement; a second concerns the study of the spectral and thermal properties of the crystals in laser condition; and a third concerns the development of innovative laser architectures and geometries. How is the project structured? FEMTOCRYBLE is a straightforward, vertical project. We proceed with growing the crystals, undertaking the laser experiment and then transferring the technology to a company. The strength of the project is based on strong collaboration between partners. Improvements in laser quality influence laser performance, which helps us to understand problems that might be encountered in future crystal generation. France is at the forefront of innovation and research in this field; why is this? There is particularly strong international competition in this field. Nonetheless, French laboratories have been positioned as one of the world leaders on crystal and laser developments for ultrashort-pulse generation based on new Ytterbium (Yb)-doped crystals. This leadership is due to a strong collaboration between French laboratories expert in material science, such as CIMAP and LCMCP, and those (such as LCF) which specialises in diode-pumped femtosecond laser devices. This national focus and leadership has already led to several important breakthroughs using very innovative Yb-doped crystals. In 2006 we developed Yb:CALGO, the shortest pulse ever obtained with an Yb-doped crystal, and undertook the first demonstration of laser operation and femtosecond pulse generation of another very promising crystal, Yb:CaF 2. Has a multidisciplinary approach proved important to FEMTOCRYBLE

Lasers femtoseconde de forte puissance moyenne à base de cristaux dopés à l'ytterbium

Ce travail de thèse concerne le développement de sources femtoseconde de forte puissance moyenne ou de forte énergie avec des matériaux pompés par diodes laser, dopés à l ytterbium. Plus particulièrement au cours de cette thèse deux types de matrices ont été utilisés, le CALGO (CaGdAlO4) et les fluorures, possédant le potentiel de générer des impulsions courtes (100aine de femtoseconde). Les caractéristiques spectroscopiques et thermiques du CALGO dopés à l ytterbium permettent d envisager le développement d oscillateur femtoseconde court de forte puissance moyenne. Dans ce contexte, la technologie des disques minces permet d obtenir avec d autres matrices, des résultats très intéressants. C est pourquoi durant cette thèse le choix de maitriser cette nouvelle technologie, avec l utilisation de ce cristal, a été fait. Dans ce cadre, des résultats très prometteurs ont été obtenus. L oscillateur femtoseconde Yb :CALGO de plus forte puissance moyenne a en effet été développé (28 W), pour une énergie non négligeable, supérieure au J et une durée d impulsions de 300 fs. Des améliorations sont à prévoir avec l utilisation de nouveaux cristaux plus dopés et plus fins, mais d hors et déjà les résultats obtenus sont au niveau de l état de l art des oscillateurs femtoseconde de forte puissance moyenne.Le cristal de CaF2 quant à lui, possède un grand intérêt pour le développement d amplificateurs énergétiques courts, puisqu il a la capacité de stocker beaucoup d énergie. Deux types d amplificateurs ont alors été développés, avec des objectifs bien différents. Le premier permet d obtenir un fort gain (~106), avec une énergie extraite proche du mJ (amplificateur régénératif), alors que le second a pour but d extraire le maximum d énergie (amplificateur multipassage), dans notre cas jusqu à 160 mJ, avec un gain plus faible (~10).Le potentiel de ces matériaux pour la génération d impulsions courtes et/ou de forte puissance moyenne a alors été démontré.This work concerns the development of high average power or high energy laser with diode-pumped ytterbium-doped materials. Two host matrices were studied, CALGO (CaGdAlO4) and fluoride, which permit the generation of ultra-short pulses. Spectroscopic and thermal properties of ytterbium doped CALGO crystals are adapted for the development of high average power oscillator. In this area, thin disk technology seems to be particularly interesting for the development of such oscillator. That s why we choose to master this technology with ytterbium-doped CALGO crystals. Thus, Yb:CALGO oscillator with the highest average power was developed (28 W), with more than J energy and pulse duration of 300 fs. Using more doped and thinner crystals should permit to improve our performances, however they are already at the state of the art of high average power oscillator.Ytterbium doped CaF2 has a great interest for short-pulse high energy amplifier, thanks to its capacity to store energy. Two types of amplifier were developed. A regenerative amplifier with high gain (~106), mJ energy level, and a multipass amplifier with lower gain (~10) but permitting to extract really high energy (up to 160 mJ).Potential of these materials for the development of short pulse high average power and/or high energy system was demonstrated.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Stable mode-locked operation of a low repetition rate diode-pumped Nd : GdVO4 laser by combining quadratic polarisation switching and a semiconductor saturable absorber mirror

International audienceIn this paper, we present the mode-locked operation of an ultrarobustly stabilised Nd:GdVO4 laser with low repetition rate by combining quadratic polarisation switching and a semiconductor saturable absorber mirror (SESAM). In addition, similar experiment was also done with Nd:YVO4. For Nd:GdVO4, 16-ps pulses at 1063nm with a repetition rate of 3.95MHz have been obtained for a laser average output power of 1.4W. For Nd:YVO4, the performance was 2.5W of average power for15-ps pulses at 1064nm. Moreover, we demonstrate experimentally the advantage of combining these two passive mode locking techniques in terms of stability ranges. We show how the dual mode-locking technique is crucial to obtain a stable and long-term mode-locked regime in our case of a diode-pumped Nd:GdVO4 laser operating at low repetition rate and more generally how this dual mode-locking technique improves the stability range of the modelocked operation giving more flexibility on different parameter

Broadband high energy diode pumped Yb:KYW multipass amplifier

International audienceWe report a diode pumped Yb:KYW amplifier delivering up to 27 mJ pulses at a repetition rate of 100 Hz and a spectral bandwidth of 5.5 nm, centered at around 1030 nm. The system is based on a double-head multipass amplifier configuration where the pump thermal load is distributed over two relatively thin laser crystals which permits a sufficiently large number of passes with minimal passive losses thus maximizing the energy extraction efficiency. The amplified pulse bandwidth theoretically supports 340 fs pulses and as a demonstration, a small fraction of the amplified pulses has been compressed to 560 fs

Efficient diode-pumped Yb3+:Y2SiO5 and Yb3+:Lu2SiO5 high-power femtosecond laser operation

International audienceWe report the mode-locked operation of two new Yb-doped oxyorthosilicates, Y2SiO5 (YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 fs with 410mW of output power at 1041 nm. More than 2.6W of average output power, for pulse durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided. These are, to our best knowledge, the highest values ever obtained and the most efficient mode-locked laser in such a classic fibercoupled diode-pumping configuratio

High-contrast Ultrabroadband Frontend Source for High Intensity Few-Cycle Lasers

An ultrabroadband seed source for high-power, high-contrast OPCPA systems at 800 nm is presented. The source is based on post compression in a hollow-core fiber followed by crossed polarized waves (XPW) filtering and is capable of delivering 80$\mu$J, 5fs, CEP-stable (0.3rad RMS) pulses with excellent spectral and temporal qualit

Compact, simple and robust cross polarized wave generation source of few-cycle, high-contrast pulses for seeding petawatt-class laser systems

International audienceA compact and robust, dual-crystal cross polarized wave generation setup combined with a hollow waveguide filter is implemented to deliver few-cycle, high-contrast laser pulses sourced from a commercial multipass Ti:Sa amplifier. The initial 25-fs pulses with a temporal contrast of 108 are shortened to 10 fs with an improved contrast of at least 10^10. The single nonlinear stage for spectral broadening and contrast enhancement of a commercial amplifier serves as an ideal injector for petawatt-class laser systems

High peak-power stretcher-free femtosecond fiber amplifier using passive spatio-temporal coherent combining

International audienceWe report on the passive coherent combining of up to 8 temporally and spatially separated ultrashort pulses amplified in a stretcher-free ytterbium-doped fiber system. An initial femtosecond pulse is split into 4 temporal replicas using divided-pulse amplification, and subsequently divided in two counter-propagating beams in a Sagnac interferometer containing a fiber amplifier. The spatio-temporal distribution of the peak-power inside the amplifier allows the generation of record 3.1 µJ and 50 fs pulses at 1 MHz of repetition rate with 52 MW of peak-power from a stretcher-free fiber amplifier and without additional nonlinear post-compression stages

Temporal cleaning of a high energy fiber-based ultrafast laser using cross-polarized wave generation

International audienceWe report the use of cross-polarized wave generation to perform both pulse shortening and temporal cleaning of a high-energy ytterbium-doped fiber-based femtosecond laser system. The nonlinear processes allow both a highly efficient nonlinear conversion of 20% and a large compression ratio of 3.5, with inherently improved coherent and incoherent contrasts. This results in the generation of 37 μJ, 115 fs pulses at a repetition rate of 100 kHz with high temporal quality

Diode-pumped regenerative Yb:SrF2 amplifier

International audienceWe report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed