Abstract

We report the results of a study of the laser-induced damage threshold of wire grid polarizers for pulsed laser radiation at 10.6 µm. The polarizers were wire grids of copper or silver deposited on ZnSe substrates and overcoated with an antireflection coating. The measurements were performed using linearly polarized, normal incident, 130-ns pulses from a hybrid CO₂ TEA laser. The laser was operated in the TEM₀₀ spatial mode and single-longitudinal mode with a pulse width of 130-ns (FWHM). The beam size at the sample was 0.36 mm (FW1/e²M). Each site was irradiated only once (one on one measurement). A damage threshold of 0.8 J/cm² (6 M W/cm²) was measured for the copper wire grid when the wires were parallel to the incident electric field (closed or low transmission condition). The damage threshold for the sample with silver wires was 2 J/cm² (15 MW/cm²) for the same orientation. The damage threshold of both samples increased by more than a factor of 2 when the wires were oriented perpendicular to the incident electric field (the open or high transmission condition). Here we have defined the damage threshold as the lowest incident fluence (or irradiance) for which damage occurred.

© 1985 Optical Society of America