Design of High Power Laser Coatings for Grazing Incidence Mirrors

Several interesting features occur for high reflectance (HR) coatings at near-grazing incidence: the existence of a Brewster's angle, a double-valued effective index for the p-polarization (enabling a MacNeille-type polarizer to be constructed in air), and a half-wave retarder. It is shown that HR coatings can be designed which have high reflectance and, as compared to normal-incidence designs, extremely low internal E-field standing waves for both s- and p-polarization components. Such mirrors should exhibit considerably less thermal distortion due to decreased laser absorption.