Acoustooptic devices provide the function of electrical to optical input transducers in many real-time optical processors of electronic signals. Particular implementations and applications emphasize modulation in space or time connected by a traveling-wave relation. Principal two-dimensional processor.s are spectrum analyzers and correlators. Multiport AO cells are useful in three-dimensional optical processing of two variables, such as frequency and phase. The performance of AO devices is limited by ef5iciency-bandwidth aperture tradeoffs which limit time bandwidths to approximately 10 for most practical devices. High efficiency devices (100%/W) have been developed for bandwidths up to approximately 600 MHz. At wider bandwidths, material attenuation and acoustooptic characteristics sharply limit efficiency, although near ideal piezoelectric transducers can be fabricated.