Alain Pellegrina

On Yb:CaF2 and Yb:SrF2 : Review of spectroscopic and thermal properties and their impact on femtosecond and high power laser performance

We present an overview of laser results we obtained with Yb-doped calcium fluoride and its isotype strontium fluoride. In order to study the laser performance in femtosecond and high power regimes, spectral and thermal properties are first discussed including the potential of these crystals at room and cryogenic temperatures. Experimental demonstrations of high-power and ultrashort pulse oscillators and amplifiers are presented and analyzed.

Broadband high-energy diode-pumped Yb:KYW multipass amplifier

We 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.

Energy-scalable temporal cleaning device for femtosecond laser pulses based on cross-polarized wave generation

We report on a compact energy-scalable device for generating high-fidelity femtosecond laser pulses based on spatial filtering through a hollow-core fiber followed by a nonlinear crystal for cross-polarized wave (XPW) generation. This versatile device is suited for temporal pulse cleaning over a wide range of input energies (from 0.1 to >10 mJ) and is successfully qualified on different ultrafast laser systems. Full characterization of the XPW output is presented. In particular, we demonstrate the generation of 1.6 mJ energy pulses starting from 11 mJ input pulse energy. The temporal contrast of the pulses is enhanced by more than 4 orders of magnitude. In addition, pulse shortening from 40 fs down to 15 fs Fourier-transform limit yields an overall peak-power transmission of up to 50%. This device not only serves as an integrated pulse contrast filter inside an ultrafast laser amplifier but also as a simple back-end solution for temporal post-compression of amplified pulses.

High-power diode-pumped cryogenically cooled Yb:CaF2 laser with extremely low quantum defect

High-power diode-pumped laser operation at 992-993 nm under a pumping wavelength of 981 of 986 nm is demonstrated with Yb:CaF₂ operating at cryogenic temperature (77 K), leading to extremely low quantum defects of 1.2% and 0.7%, respectively. An average output power of 33 W has been produced with an optical efficiency of 35%. This represents, to the best of our knowledge, the best laser performance ever obtained at such low quantum defects on intense laser lines.

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

A 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 efficient XPW generation for high contrast high energy ultrashort laser pulses

Cross polarized wave generation (XPW) is a well established technique for contrast enhancement of ultrashort pulses in high energy laser systems [1]. Efficient conversion with XPW only occurs at high intensities. Weaker, unconverted pre and post pulses are thus rejected by the second polarizer, thereby improving the temporal contrast of the pulse. XPW has several drawbacks especially in terms of simultaneously achieving high conversion efficiencies and output energies. Limitations in seeding the nonlinear filter with high energies arise from the upper intensity limit of white light generation while high conversion efficiencies require excellent beam quality.

Compact and robust cross polarized wave generation source for seeding petawatt-class laser systems

A Ti:Sa amplifier (1.2 mJ, 25 fs, CR=10^8) and dual-crystal cross polarized wave generation setup is demonstrated to deliver few-cycle, high-contrast pulses (10 fs, CR>10^10) appropriate for seeding a multi-petawatt laser system.

Yb-doped-based High Energy and Broadband Multipass Amplifiers at 100 Hz

A 27mJ diode pumped multipass Yb:KYW amplifier at 100Hz with 5.5nm bandwidth at 1030nm is presented. First results on the subsequent Yb:CaF2 power amplifier stage are also presented resulting 51mJ at 20Hz.

High-fidelity frontend based on XPW filter for high-contrast few-cycle OPCPAs

We demonstrate a 80μJ, 5fs, CEP-stable injector with high spectro-temporal quality. The device relies on post-compression in a hollow-core fiber followed by XPW filtering and is an ideal seed for high-power high-contrast OPCPA systems.

High energy and efficient cross polarized wave generation for high contrast ultrashort laser sources

We present a compact and energy-scalable ultrashort laser setup based on waveguide filtering and cross polarized wave generation. A 650 µJ, 15.5 fs, 10-10 contrast ratio XPW pulse is produced with 3.3 mJ, 25 fs input pulses