High-resolution, high-speed photorefractive incoherent-to-coherent optical converter

We demonstrate a photorefractive incoherent-to-coherent optical converter driven by ultraviolet light that provides a 35-mu s response time and an optical resolution of 124 line pairs/mm. The device, implemented in KNbO3, operates with a modulating intensity of 85 mW/cm(2), which corresponds to an optical switching energy per bit of 0.5 pJ. A conversion rate of the order of 90 Gbits/(s cm(2)) is achieved. The conversion between the ultraviolet light and the visible laser beam at lambda = 532 nm occurs through anisotropic Bragg diffraction at a modulated interband photorefractive grating. Our device has a better optical resolution and conversion rate than optically addressed solid-state spatial light modulators based on the photorefractive effect and multiple quantum wells, and it is also faster than devices based on liquid crystals. (C) 1999 Optical Society of America OCIS codes: 330.6120, 070.4550, 160.5320, 090.7330.