We demonstrate the wave-front correction of the LULI 100TW, 300 fs/30 J high power laser facility for a sequence of shots. Excellent beam focusability close to diffraction limit has been obtained using an adaptive optic system, composed of a large aperture dielectric coated deformable mirror and a home-made shearing interferometer. This correction allows to produce reproducible focal spots with Strehl ratios close to 0.9 at a repetition rate of a shot every 20 minutes, despite of wave front distortions generated by cumulative thermal effects in the large disc amplifiers.
We have implemented on the LULI 100 TW laser facility a closed-loop Adaptive Optics system composed of a large aperature dielectric coated deformable mirror and a home-made shearing interferometer. Significant results have been obtained with this system: not only the beam focusability has been improved to a Strehl ratio of 0.9 but it has also been kept at this level for a sequence full-energy shots, with a repetition rate of 20 minutes, through systematic compensation of the cumulative thermal load generated in the large disk amplifiers.
We have implemented on one beam of the LULI six-beam high-energy (6×100 J, 1 ns) Nd:glass laser facility a closed-loop Adaptive Optics (AO) system to compensate for thermal distortions onto the wave front. Using the AO system composed of a dielectric coated deformable mirror and of a wave front sensor, we are able to improve the wave front quality in order to obtain a focal spot close to the diffraction limit. This allows not only to improve the reproducibility of the experiments but also to increase by at least two orders of magnitude the peak intensity as compared with what usual laser smoothing techniques can achieve.
We show wave front correction of a 300 fs/60J laser pulse serie. This correction is based on an optically addressed liquid crystal optical valve (OASLM) which induces high resolution phase modulations. When performed before complete thermal relaxation of the laser Nd:glass amplifiers, this correction allows to increase the system repetition rate by a factor three.
Volume holographic gratings and ion-etched dielectric diffraction gratings have been designed with the goal of improving the efficiency and damage threshold when used in CPA laser compression scheme. Two damage threshold measurement techniques have been implemented, including one method based on the statistical distribution of damage fluences. We first tested samples with submillimeter laser spots in the subpicosecond regime. We could demonstrate large sample gratings in a complete CPA configuration with over 96% efficiency per pass and a damage threshold twice the one observed on gold coated gratings.
We have developed a high resolution programmable adaptive optic device based on an optically-addressed liquid crystal electro-optical valve (OALEV) controlled by an achromatic three-wave lateral hearing interferometer (ATWLSI). This loop, which can work at 4 Hz, corrects the wavefront of our 100-TW Nd:Glass. Beyond this application, we were able to generate high resolution programmable phase plates to shape the far- field pattern of low-energy cw-lasers as well as high power lasers.
We have implemented a Ti:sapphire/mixed Nd:glass laser syste at LULI producing sub-picosecond pulses in the 100 TW power range. Focusing to a 1.5-times diffraction-limited spot results in a peak intensity on target over 1019 W/cm2. Significant experiments in particle acceleration, X-ray laser and other basic plasma physics researchers have been carried out since this implementation. This paper details the characteristics of the present set-up and the main path of progress towards a high performance petawatt facility.
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