Refractive index nonuniformities in acousto-optic devices due to heat production by ultrasound

The effect of heat in acousto-optic devices is a persistent problem with respect to the electric, acoustic and optical behavior of the device. The temperature differences across the acousto-optic crystal driven at acoustic power levels up to 1 W, common for operation of these devices, can reach values of 90-100 °C that cause significant refractive index nonuniformities, severely influencing optical performance of these devices. In this paper, we present a simple and effective physical model of the heat generation due to acoustic absorption in the device and calculate the temperature distribution that influences the optical parameters. We compare the modeling results with temperature distribution measurements on acousto-optic crystals of different configurations. The changes in refractive indices are also calculated.