Auto-collimation diffraction of two-dimensional metal-dielectric grating with azimuth angle of 45°

Grating under auto-collimation configuration with polarization-independent high diffraction efficiency plays an important role in the displacement measurement system, spectral beam combining system and so on. In this paper, we proposed, for the first time, a reflective two-dimensional metal-dielectric grating of which the (-1, -1) order beam is diffracted back along the input light direction, when the incident azimuth angle is 45°. With optimized structure, the (-1, -1) order diffraction efficiencies of transverse electric polarization (TE) and transverse magnetic polarization (TM) are 95.01 % and 95.04 % at incident wavelength of 632 nm, respectively. The structure based on the frustum of a cone performs well in manufacturing tolerance, which provides possibility for practical applications. A grating is fabricated experimentally in this research. The high efficiencies of TE and TM polarization have great application potential in 2D displacement measurement technique and high power laser systems.