Effect on Diffraction Efficiency of Diffractive Optics with Consideration of Surface Roughness

Based on the expression of phase delay of the multi-layer diffractive optical elements, the mathematical model of diffraction efficiency and polychromatic integral diffraction efficiency under the influence of single-point diamond turning is proposed, and the analytical expressions are correspondingly provided. The application of the multi-layer diffractive optical elements whose substrates are composed of ZnSe and ZnS for each layer is simulated and analyzed in near-infrared waveband (1.4 similar to 2.5 m). The results show that the surface roughness error leads to a decrease in the diffraction efficiency and the polychromatic integral diffraction efficiency of the multilayer diffractive optical elements, making the imaging quality of the hybrid imaging optical system decreased. Therefore, when the single-point diamond turning is used to cut optical elements, the result is instructive to draw out justified limit surface roughness error according to usage requirements.