High-Resolution Optical Novelty Filter Using Photorefractive GaAs And High-Speed Nematic Liquid Crystal Phase Modulator

Recently, optical novelty filters [1] have attracted much attention because of their potential applications in motion detection and optical tracking. Most optical novelty filters reported to date use BaTiO3 crystal as the needed nonlinear medium. In a previous report [2], we have shown that, owing to the shorter response time of GaAs, the output resolution of a GaAs based optical novelty filter is potentially much higher than that of a BaTiO3 based optical novelty filter. However, a relatively high-speed spatial phase modulator is needed for such an implementation. As a result, the usual nematic liquid crystal (NLC) modulators used in other implementations of optical novelty filter would respond too slow for the current implementation. Nevertheless, recently, the speed of NLC modulator has been greatly improved by various methods. For example, using the transient nematic effect, a frame time of less than 50 μs have been demonstrated [3]. Such a frame time is more than adequate for the current implementation. In this paper, we report the result of an investigation on the potential of building a high-resolution optical novelty filter using photorefractive GaAs and high-speed nematic liquid crystal phase modulator.