Jean-Paul Chambaret

10 ?10 temporal contrast for femtosecond ultraintense lasers by cross-polarized wave generation

We take advantage of nonlinear properties associated with chi(3) tensor elements in BaF2 cubic crystal to improve the temporal contrast of femtosecond laser pulses. The technique presented is based on cross-polarized wave (XPW) generation. We have obtained a transmission efficiency of 10% and 10(-10) contrast with an input pulse in the millijoule range. This filter does not affect the spectral shape or the phase of the cleaned pulse. It also acts as an efficient spatial filter. In this method the contrast enhancement is limited only by the extinction ratio of the polarization discrimination device.

Aberration-free stretcher design for ultrashort-pulse amplification

A novel aberration-free pulse stretcher design is presented. This system permits the stretching of a 30-fs pulse to 300 ps and recompression to a duration of 33 fs, limited by the spectral clipping.

Characterization of electron beams produced by ultrashort (30 fs) laser pulses

Detailed measurements of electron spectra and charges from the interaction of 10 Hz, 600 mJ laser pulses in the relativistic regime with a gas jet have been done over a wide range of intensities (1018–2×1019 W/cm2) and electron densities (1.5×1018–1.5×1020 cm−3), from the “classical laser wakefield regime” to the “self-modulated laser wakefield” regime. In the best case the maximum electron energy reaches 70 MeV. It increases at lower electron densities and higher laser intensities. A total charge of 8 nC was measured. The presented simulation results indicate that the electrons are accelerated mainly by relativistic plasma waves, and, to some extent, by direct laser acceleration.

Design and demonstration of a high-energy booster amplifier for a high-repetition rate petawatt class laser system

We have successfully developed a high-energy, high-repetition rate Ti:sapphire laser system that delivers 33 J before compression at 0.1 Hz. The final booster amplifier is based on a 100 mm diameter Ti:sapphire crystal pumped with 72 J of energy in six beams delivered by three frequency-doubled high-repetition rate Nd:glass lasers. This system is, to the best of our knowledge, the first demonstrated petawatt class laser system running at a high repetition rate.

High-efficiency, simple setup for pulse cleaning at the millijoule level by nonlinear induced birefringence.

Nonlinear elliptical polarization rotation is used to improve the contrast of femtosecond pulses by several orders of magnitude. Using nonlinear induced birefringence in air, we produced cleaned pulses with an energy of a few hundreds of microjoules. This technique presents several major advantages, such as convenience and stability of the setup. We investigated the phase profile required for obtaining high-energy pulses. No phase distortion is observed, and the spatial quality of the beam is preserved.

Generation of 25-TW, 32-fs pulses at 10 Hz

We have developed a femtosecond laser chain that generates 25-TW pulses of less than 35 fs at 10 Hz with focused intensities higher than 5 x 10(19) W/cm(2) and an average power of 8 W. This system is optimized for a broad transmission bandwidth and includes an aberration-free stretcher compressor.

High-efficiency, broad band, high-damage threshold high-index gratings for femtosecond pulse compression.

High efficiency, broad-band TE-polarization diffraction over a wavelength range centered at 800 nm is obtained by high index gratings placed on a non-corrugated mirror. More than 96% efficiency wide band top-hat diffraction efficiency spectra, as well as more than 1 J/cm(2) damage threshold under 50 fs pulses are demonstrated experimentally. This opens the way to high-efficiency Chirped Pulse Amplification for high average power laser machining by means of all-dielectric structures as well as for ultra-short high energy pulses by means of metal-dielectric structures.

Search for stimulated photon-photon scattering in vacuum

Abstract:We have searched for stimulated photon scattering in vacuum at a center of mass photon energy of 0.8 eV. The QED contribution to this process is equivalent to four wave mixing in vacuum. No evidence for scattering was observed. The corresponding upper limit of the cross-section is .

Broadband femtosecond infrared parametric amplification in β-BaB 2 O 4

Infrared femtosecond pulses of 100 μJ of energy are generated in a two-stage, triple-pass, type I β-barium borate parametric amplifier. A focusable intensity of 5 × 1012 W/cm2 with an f/20 optic is demonstrated.

High-power diode-pumped Yb:GdCOB laser: from continuous-wave to femtosecond regime

Abstract We present an efficient tunable continuous-wave diode-pumped Yb 3+ :Ca 4 GdO(BO 3 ) 3 (Yb:GdCOB) laser producing at room temperature up to 3.2 W average power with a slope efficiency of 80% when pumped with a 10 W laser diode. A large tunability from 1017 to 1086 nm is obtained. The broad emission spectrum has been used to develop a diode-pumped Yb:GdCOB femtosecond laser. The laser generated 90 fs pulses, at a center wavelength of 1045 nm. By using a semiconductor saturable absorber mirror (SESAM) for the mode locking, the average power was 40 mW and the repetition rate of 100 MHz.