A theoretical analysis of acoustooptical pulse modulators is given. Calculations are carried out that yield the intensity and rise time of the scattered light. The optimum relationship between the dimensions of the optical and acoustic beam is given. A fast high-efficiency modulator has been built based on the theoretical results. The modulator is composed of a 350-MHz ZnO transducer sputtered on a quartz acoustic lens and an As2S3glass serving as the modulating material. With 0.6 watt of electrical RF peak power driving the modulator, 70 percent of the light intensity (at 0.63μ) is deflected. The rise time of the scattered light pulse is of the order of 6 ns.