High-Speed and High-Contrast Spatial Light Modulator that Uses Electroabsorption in a GaAs Single Crystal

A new spatial light modulator that uses electroabsorption induced by the Franz-Keldysh effect in a GaAs single crystal is proposed. The device has the same structure as the Pockels readout optical modulator, is driven by a high ac voltage, and is operated in the superprime mode. Its high-frame-rate (over 500-Hz) operation, high contrast ratio (350:1), and large gamma characteristics (2.47) were experimentally confirmed in the transmission mode, although its operating-wavelength (readout) region is restricted to a narrow band near the band gap. In the reflection mode, however, this device has a high contrast ratio and large gamma characteristic (approximately 5), offering the possibility of its use as a nonlinear device.