Optical performance of bimetallic mirrors under lateral temperature distributions

Abstract

The optical performance evaluations for various mirror shapes due to lateral temperature distributions were conducted using the finite element analysis program, SDRC-IDEAS. In this study, bimetallic effects with two different plating materials (nickel and aluminum) were considered for aluminum mirrors and beryllium mirror substrates. Lateral temperature distributions used in this thermal analysis, are cases of linear, quadratic and cubic variations. The optical surface deformations were reduced in terms of Zernike coefficients by the program PCFRINGE. Additionally, corrected surface deformations after piston, tilts, and focus removed were calculated. It was found that the optical performances of bimetallic mirrors strongly depend on the plating material, plating thickness, and the mirror substrate shapes. The results indicate that there does not exist a definitive common rule for the optimum. A detailed analysis as presented herein is generally required to adequately predict the bimetallic effects.