Highly tolerant, high-efficiency pulse compressor gratings for high-power lasers

In this work, we present our research findings on high-efficiency pulse compression gratings (PCGs) operating in reflection and designed for high-power lasers. Our primary objective is to develop robust designs that withstand fabrication tolerances while maintaining a diffraction efficiency exceeding 99% over a spectral bandwidth of at least 20 nm around the central wavelength of the laser. Moreover, a key challenge in the development of PCG is ensuring their ability to sustain high energies and high peak powers (i.e. a relatively high laser-induced damage threshold (LIDT)). For this, we propose and approach based on reflective grating waveguide structures, where high diffraction efficiency is achieved through destructive interference in the specular reflection. This, however, demands precise design of the grating parameters (period, groove depth, and duty cycle) as well as the thicknesses of the coated material pairs (e.g., Ta₂O₅/SiO₂ or HfO₂/SiO₂). During the presentation, we will discuss the detailed design methodology; analyze the impact of structural parameters on PCG performances optimized for laser emitting at wavelength of 1030 nm, and present first experimental validation.