Absorptance of IR Laser Radiation at a Metallic Interface at Various Angles of Incidence and Polarizations.

摘要

A calorimetric method is developed to measure the absorptance of IR laser radiation at a metallic interface. The absorptance of Al and Ti is measured at various angles of incidence (10 to 87 deg) and laser polarizations (parallel, perpendicular, and random relative to the plane of incidence). Designing the metal surface to be approximately the size of the beam and using a thin (0.032 in.) sample facilitate the simplifying assumptions. The average incident power is 13 w/sq.cm. For the laser polarizations, parallel and perpendicular, the maximum difference between theoretically and experimentally calculated values is 26 percent and 57 percent respectively for Al and 100 percent and 500 percent respectively for Ti. The Ti values are largely attributed to surface roughness (sanded) and oxidation. Without a Brewster window in the laser cavity, a test revealed the laser polarization was not 50 percent horizontal and 50 percent vertical. The average polarization is 17 percent horizontal and 83 percent vertical. (Author)