A Review of Acoustooptical Deflection and Modulation Devices

A review of the principles of acoustooptical devices is given. Some very simple momentum conservation considerations indicate the optimum relationship between the optical and acoustic beam dimensions for various functions such as scanning or modulation. A calculation for the usual type of acoustic amplitude modulation is described, and serves as an example of the type of detailed considerations that are necessary and possible, as well as a verification of the validity of the simple momentum considerations. It is shown that the product of the fraction of the light that may be scattered and the bandwidth for Bragg scattering equals a materials constant times the acoustic power. This relationship is shown to be valid even to the extent of numerical constants for several configurations allowing a trade-off between these parameters. Thus, the required modulation power for any level of device performance is easily determined. The details of acoustic deflection under conditions of acoustic beam focusing or scanning are also given.