Ultra-broadband polarization-independent high-efficiency transmission grating based on three-layer dielectric rectangle groove

We report on an ultra-broadband three-layer dielectric transmission rectangle-groove grating with polarization-independence and high diffraction efficiency for -1st order under Littrow incidence. The all-dielectric grating consists of triple-layer grating ridges placed on the fused silica substrate. Next, the diffraction process is analyzed by using a simplified mode method and optimized parameters of the grating structure are calculated by using rigorous coupled analysis and a simulated annealing algorithm. The theoretical -1st order efficiencies of the transmission grating are more than 95% with incident wavelength ranging from 1446-1641 nm and incident angle ranging from 32.1-42.7 degrees for both TE and TM polarizations, respectively. We also discuss that the great fabrication tolerances that depend on grating period and the thicknesses of the three dielectric layers ensure the high performance of the designed grating in the fabrication process. With the properties of ultra-broadband, high efficiency and polarization-independence, the designed rectangular all-dielectric grating should be of great interest for the most practical applications of dispersion.