Thermal design for germanium acoustooptic modulators

The germanium acoustooptic modulator is often used to modulate the output of CO(2) lasers for laser radar applications. With the ever increasing power of commercially available CO(2) lasers it is of interest to determine the thermal and optical limits for these modulators. In this paper the optical and acoustic absorption phenomena occurring in germanium are described. Various sources of heat are identified, particularly that due to transducer loss. It is shown how the temperature distribution and the runaway threshold can be determined in typical modulators. As an example the temperature distribution and threshold are determined for the Mullard AOM 100 acoustooptic modulator.