POLARIZATION-DEPENDENT ANGULAR REFLECTANCE OF SILICON AND GERMANIUM IN THE INFRARED

We have investigated the reflectance of crystalline silicon and german ium samples for infrared radiation polarized parallel and perpendicula r to the plane of incidence. A Fourier transform infrared (FT-IR) spec trometer was employed to measure the specular reflectance at angles of incidence from 20 degrees to 60 degrees in the wavelength range betwe en 2 mu m and 25 mu m The measurements agree with the theoretical anal ysis to within the experimental uncertainty. At large angles of incide nce, the reflectance depends strongly on polarization. Since the beam in a spectrometer generally exhibits partial polarization, the measure d reflectance without a polarizer may differ from the average reflecta nce for the two polarization states. This work demonstrates that silic on and germanium can be used as standard reference materials for specu lar reflectance in the mid-infrared region.