1200 lines/mm Gold-Coated pulse compression grating for 850–970 nm

Abstract

The structural parameters and spectral performance of the pulse compression gratings are directly related to the design and output quality of high-power laser systems. In this paper, for the gold-coated gratings applicable to the 850–970 nm wavelength range, the effects of variations in groove density, incident angle, and out-of-plane angle on their diffraction efficiency and bandwidth were calculated and analyzed. Subsequently, the variation laws of diffraction efficiency and bandwidth of the 1200 lines/mm gold-coated grating with structural parameters were simulated and analyzed, with a focus on the diffraction efficiency variation at the 850 nm short wavelength, which is more sensitive to structural parameters. For the 1200 lines/mm grating, the simulated average diffraction efficiency over the 850–970 nm wavelength range under the out-of-plane Littrow geometry (α = α_L, γ = 10°) is almost equal to that under the in-plane geometry (α = α_L + 12°, γ = 0°), with a difference of only 0.04%. Finally, by adopting holographic interference exposure technology and magnetron sputtering coating technology, a 1200 lines/mm gold-coated grating was successfully fabricated, which had an average diffraction efficiency of 91.4% in the 850–970 nm wavelength range. The aperture of this gold-coated grating is 320 mm × 230 mm, and the area-scanned average diffraction efficiencies corresponding to the single wavelengths of 850 nm, 910 nm, and 970 nm are 85.5%, 91.8%, and 91.8%, respectively.