The results of glancing incidence absorptance measurements performed on diamond-turned copper mirrors are presented. A photoacoustic calorimetry technique is used in which the output from a low power, chopped cw Nd:YAG laser (1.06 μm) is incident upon the mirror at angles of incidence from 0 to 87°, for both s and p-polarizations. Measurements are obtained as a function of the diamond turning groove orientation with respect to the plane of incidence. Minimum absorptance, at high angles of incidence, is achieved with s-polarized light and with the grooves aligned parallel to the plane of incidence. The affects on the absorptance of a large scratch at glancing incidence are also described.
Wayne D. Kimura,
Theodore T. Saito,
"Measurements Of Diamond-Turned Copper Mirrors At Glancing Incidence", Proc. SPIE 0751, Reflective Optics, (10 June 1987); doi: 10.1117/12.939896; https://doi.org/10.1117/12.939896