Pulse compressor grating-waveguide structure for high-power chirped pulse amplification at wavelengths around 2 µm

We present a concept and the demonstration of a high-efficiency pulse compressor grating operating in reflection and designed for high-power laser systems at wavelengths of about 2 µm. The design provides a theoretical diffraction efficiency of >99% over a spectral bandwidth of 42 nm centered at a wavelength of 2050 nm. A comprehensive tolerance analysis was conducted for key fabrication parameters (groove-depth, duty-cycle, and sidewall angle of the grating) and refractive index variations of the dielectric layers. The theoretical laser-induced damage threshold is estimated to be >0.68 J/cm² for 500 femtosecond pulses, indicating that the grating can withstand relatively high pulse energies and peak powers. Experimental characterization of the fabricated sample yielded a diffraction efficiency of 97%, which, to the best of our knowledge, is the highest reported to date for a 2 µm pulse compressor grating.