Polarization dependence of laser damage growth features on multilayer dielectric mirrors for petawatt-class lasers.

PETAL (Petawatt Aquitaine Laser) is an ultrahigh-power laser dedicated to academic research that delivers sub-picosecond pulses. One of the major issues of these facilities is the laser damage on optical components located at the final stage. Transport mirrors of the PETAL facility are illuminated under different polarization directions.

Investigation of the influence of a spatial beam profile on laser damage growth dynamics in multilayer dielectric mirrors in the near infrared sub-picosecond regime.

Laser-induced damage growth has often been studied with Gaussian beams in the sub-picosecond regime. However, beams generated by high-power laser facilities do not feature Gaussian profiles, a property that raises questions concerning the reliability of off-line laser-induced damage measurements. Here, we compare laser-induced damage growth dynamics as a function of beam profiles.

Impact of compression grating phase modulations on beam over-intensities and downstream optics on PETAL facility.

Chirped pulse amplification has been widely implemented in high power laser chains. It consists of a set of diffraction gratings used to stretch and compress short laser pulses. In the case of high power laser chains, the compression stage is followed by the transport mirror in order to carry the laser beam to its final target.

Influence of absorption-edge properties on subpicosecond intrinsic laser-damage threshold at 1053 nm in hafnia and silica monolayers.

Owing to their relatively high resistance to laser-induced damage, hafnia and silica are commonly used in multilayered optical coatings in high-power laser facilities as high- and low-refractive-index materials, respectively. Here, we quantify the laser-induced-damage threshold (LIDT) at 1053 nm in the short-pulse regime of hafnia and silica monolayers deposited by different fabrication methods, including electron-beam evaporation, plasma ion-assisted deposition and ion-assisted deposition. The results demonstrate that nominally identical coatings fabricated by different deposition techniques and/or vendors can exhibit significantly different damage thresholds.

Robust optimization of the laser induced damage threshold of dielectric mirrors for high power lasers.

We report on a numerical optimization of the laser induced damage threshold of multi-dielectric high reflection mirrors in the sub-picosecond regime. We highlight the interplay between the electric field distribution, refractive index and intrinsic laser induced damage threshold of the materials on the overall laser induced damage threshold (LIDT) of the multilayer. We describe an optimization method of the multilayer that minimizes the field enhancement in high refractive index materials while preserving a near perfect reflectivity.

1.15 PW-850 J compressed beam demonstration using the PETAL facility.

The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline.

Laser damage growth with picosecond pulses.

Laser-induced damage growth has been investigated in the subpicosecond regime at 1030 nm. We have herein studied the growth of damage sites initiated on a high-reflective dielectric coating under subsequent laser irradiations at a constant fluence. We show through an experimental approach that growth can be triggered for fluences as low as 50% of the intrinsic damage threshold of the mirror.

Assessment of mono-shot measurement as a fast and accurate determination of the laser-induced damage threshold in the sub-picosecond regime.

Standard test protocols need several laser shots to assess the laser-induced damage threshold of optics and, consequently, large areas are necessary. Taking into account the dominating intrinsic mechanisms of laser damage in the sub-picosecond regime, a simple, fast, and accurate method, based on correlating the fluence distribution with the damage morphology after only one shot in optics is therein presented. Several materials and components have been tested using this method and compared to the results obtained with the classical 1/1 method.

Laser damage density measurement of optical components in the sub-picosecond regime.

A rasterscan procedure adapted to the sub-picosecond regime is set to determine laser-induced damage densities as function of fluences. Density measurement is carried out on dielectric high-reflective coatings operating at 1053 nm. Whereas laser-induced damage is usually considered deterministic in this regime, damage events occur on these structures for fluences significantly lower than their intrinsic damage threshold.

Experimental demonstration of a synthetic aperture compression scheme for multi-Petawatt high-energy lasers.

We present the experimental demonstration of a subaperture compression scheme achieved in the PETAL (PETawatt Aquitaine Laser) facility. We evidence that by dividing the beam into small subapertures fitting the available grating size, the sub-beam can be individually compressed below 1 ps, synchronized below 50 fs and then coherently added thanks to a segmented mirror.

High reflection mirrors for pulse compression gratings.

We report an experimental investigation of high reflection mirrors used to fabricate gratings for pulse compression application at the wavelength of 1.053microm. Two kinds of mirrors are studied: the mixed Metal MultiLayer Dielectric (MMLD) mirrors which combine a gold metal layer with some e-beam evaporated dielectric bilayers on the top and the standard e-beam evaporated MultiLayer Dielectric (MLD) mirrors.

Effect of electric field on laser induced damage threshold of multilayer dielectric gratings.

This paper studies gratings engraved in multilayer dielectric stacks for ultra high intensity laser compressors application. We design various grating profiles with high reflected efficiencies for 1780 l/mm multilayer dielectric gratings (MLD). Each grating is defined to exhibit a different electric field maximum value in the pillars of the grating.