Design and analysis of broadband high-efficiency pulse compression gratings.

We report on two effective methods, multiparameter optimization and local optimization combined with the diffraction bandwidth merit function, to design a broadband pulse compression grating (PCG), and we present broadband, high-efficiency PCGs based on both the multilayer dielectric grating (MDG) and metal-multilayer dielectric grating (MMDG) models. For MDG, the average diffraction efficiency is higher than 97.5% for TE polarization light over the 100 nm bandwidth centered at 800 nm. Moreover, a novel multilayer structure, which comprises higher index material in the high-reflectivity mirror and relatively lower index material on top, is first proposed to yield higher average efficiency, broader bandwidth, and excellent fabrication tolerance. For MMDG, it exhibits an ultrabroadband top-hat diffraction spectrum with average efficiency exceeding 97% over the 200 nm wavelength wide centered at 1053 nm. In addition, the MMDG structure, which has the best tolerance for grating fabrication, is determined by investigating characteristics of MMDGs with different thin-film structures.