Abstract

Compared with the conventional oxide photorefractive crystals, the main advantages of GaAs are the short response time (submilliseconds at about 1 W/cm² write beam intensity), the availability of large-size crystals, and the compatibility with other semiconductor devices such as near-infrared semiconductor lasers. In this paper, a realtime VanderLugt optical correlator is demonstrated using a GaAs crystal as the dynamic volume holographic medium and liquid crystal spatial light modulators (SLMs) as the input devices. The advantage of using the VanderLugt configuration here is that the reference image (located in the read beam) can be changed at a rate not limited by the response time of the dynamic holographic medium; thus the size and orientation invariance can be, in principle, achieved in real time by displaying many different orientations and sizes of a reference image in a very short period. The potential system frame rate, limited by the response time of the photorefractive GaAs crystal, can be a few kHz or higher, depending on the total write beam intensity. The limitations of this optical correlator will be discussed.

© 1990 Optical Society of America