Technology of anti-reflection coating of KDP crystal by using Fourier modal method

The effects of the period and amplitude of micro-waveness on KDP surface processed by single point diamond turning(SPDT) on the refractive index, thickness, and transmittance of single-layer anti-reflection (AR) coating were analyzed by the Fourier modal method. It is found that the optimal refractive index of the AR film is about 1.22, and the thickness should be 180 to 220 nm in order to ensure the transmittance of more than 99% in the optimal refractive index condition. The period and amplitude of micro-waveness on the surface of KDP crystal do not generally affect the values of the optimal refractive index and the reasonable thickness range of single-layer AR coating. Just considering the practical range of the period and amplitude of micro-waveness, the transmittance is not affected b