Acoustooptical modulation allows us to manipulate light beams, either laser or incoherent, in response to an electrical input signal to a piezo-electric transducer bonded to the appropriately fabricated crystal. An acoustic beam launched at the transducer into the crystal generates a periodic modulation of the refractive index that behaves as a phase grating whose spacing is the acoustic wavelength. The important elastooptic properties of acoustooptic device materials include the refractive indices, the acoustic wave propagation velocities for both longitudinal and shear modes for the principal crystallographic directions, the photoelastic coefficients, and the acoustooptic figure of merit corresponding to the most favorable configurations. Two recently synthesized classes of crystals have been identified as having outstanding properties for applications in acoustooptic devices. Crystals of lead chloride and lead bromide were recently identified in the Soviet Union as having superior acoustooptic properties, with good potential for devices.