Acousto‐Optic Properties of Crystalline Germanium

The acousto‐optic properties of crystalline germanium have been measured, including a complete and accurate characterization of the photoelastic tensor. The results of this work indicate that germanium has a substantially larger acousto‐optic figure of merit, (n6p2/ρV3), than other known infrared materials, with the exception of crystalline tellurium. Because germanium has superior optical and mechanical properties, it should be preferred to tellurium for many infrared modulation and deflection applications. In addition, we propose that germanium be used as a standard for future infrared acousto‐optic material studies in the same way that fused silica has been used in the visible and near visible portion of the spectrum.