We report the generation of unprecedented 10 PetaWatt laser pulses obtained from each of the two beamlines of the High Power Laser System (HPLS) of ELI-NP (Extreme Light Infrastructure – Nuclear Physics) research infrastructure. The laser system is a hybrid system made of a double CPA based on amplification within Titanium Sapphire crystals combined with an OPCPA with a parametric amplification stage boosting the energy to 10 mJ at the entrance of the second CPA. A XPW filter is also inserted between the two CPA and in combination with the OPCPA improves the temporal contrast of the pulses by typically 7 orders of magnitude. The spectral effects occurring during amplification such as gain narrowing and wavelength shifting are compensated through the use of spectral filters. Final amplification stages are involving large aperture Ti:Sapphire crystals (up to 200 mm) which are pumped by high energy frequencydoubled Nd:Glass lasers delivering each 100 J of green light. Laser beams have been amplified respectively up to 332 J and to 342 J of pulse energy at 1 shot per minute without any occurrence of ASE and transverse lasing thanks to index matching fluid surrounding the crystal over is entire length and pump deposition management over the time before each beam pass within the Ti:Sapphire crystal. We have demonstrated full aperture compression by metric gratings of these amplified pulses down to 22.6 fs and therefore made the full demonstration for the first time ever of 10 PW capability from a laser system.
We propose a control technique for laser induced sub- micron ripples on titanium and silicon using femtosecond laser
pulse shaping. This is based on a real-time observation method of nano ripples by diffraction of UV laser beam and
programmable pulse temporal design. The feedback diffraction signal provided information of ripples’ period, area,
direction, and arrangement uniformity. By using a genetic algorithm optimization, ripples formation was optimized for
their period tuning ability and their uniformity. The diffraction signals were validated with scanning electron microscope
(SEM) images. At the generation wavelength of 800 nm and depending on the pulse form, ripples on titanium show
periods from 610 nm to 680 nm, and ripples on silicon has periods from 710 – 770 nm. Laser pulse energy affects
optimization due to transient energy deposit on material with pulse form effects in the threshold fluence and ripple
areas.
An automated test station to measure the laser-induced damage threshold (LIDT) according to ISO 21254-1,2,3,4:2011
standards is presented. The laser is a single longitudinal mode, 500 mJ, 6 ns, Q-switched, 10 Hz, linearly polarized, 1064
nm laser, with 2-nd and 3-rd harmonic capabilities. The machine is able to operate the S-on-1 test (S = 500), or the Type
2 endurance (durability) test. The main blocks of the station are described, emphasizing some original solutions.
Preliminary results of LIDT measurements using the S-on-1 test on several coatings and on uncoated fused silica
substrates with various degrees of roughness are also presented.
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