Photoacoustic measurements of surface and bulk absorption in HF/DF laser window materials.

A new photoacoustic technique is used for quantitatively determining surface and bulk absorption losses at HF/DF laser wavelengths. Materials investigated include Si, GaAs, ZnSe, Al(2)O(3), MgO, MgF(2), CaF(2), SrF(2), BaF(2), LiF, and KMgF(3). Although several materials show predicted intrinsic bulk absorption at 3.8 microm, no material is found to exhibit predicted intrinsic absorption loss at 2.7 microm. High surface absorption at both HF and DF laser frequencies general ly dominate over-all absorption losses for most of the materials tested.