Design of ultra-wide-angle beam splitter

Diffractive optical elements (DOE) are widely used in modern optical systems due to their advantages of small size, light weight, high design freedom, wide material selectivity and unique dispersion performance PD. However, with the development of technology, the optical system has put forward higher requirements on larger diffraction angle, high diffraction efficiency and uniformity of DOEs. According to the grating equation, the diffraction angle can only be increased by reducing the feature size of DOE. When the feature size of the DOE is below the sub-wavelength level, the conventional scalar diffraction theory is no longer applicable. In this paper, an ultra-wide-angle 1 x 11 beam splitter is designed by using one-dimensional rigorous coupled-wave theory and genetic algorithm. The maximum diffraction angle of the beam splitter can be reach 72 degrees and the diffraction efficiency is 92.98% with the uniformity error is 5.77%. By comparing with the FDTD simulation results, the difference in the diffraction efficiency of the DOE designed based on this method is less than 1%. This method has wide application prospects in the design of large angle beam splitters, structural light generation, holographic projection display and other fields.