Interband photorefractive effects in KNbO3 induced by ultraviolet illumination

High-frame-rate joint Fourier-transform correlator based on Sn(2)P(2)S(6) crystal

We present a joint Fourier-transform correlator working at a 10-kHz repetition rate. It is based on a photorefractive Sn(2)P(2)S(6) crystal operated in the pulsed direct band-to-band photoexcitation regime at a wavelength of 532 nm and a pulse length of 50 ns. The intersection of two plane waves with a total pulse fluence of 100muJ/cm(2) results in a buildup of thin dynamic holograms to a typical diffraction efficiency of 10(-4) in a time of ~1mus and decay again in less than 10mus . The correlator was tested by a fast image sequence generated by the pulsed readout of a holographic memory system. Successful correlation at a rate of 10 kHz has already been achieved for a pulse energy of only 200 nJ in the template images.

Fast, reconfigurable light-induced waveguides

Fast and reconfigurable one-dimensional waveguides are produced by interband photorefraction. The index barriers are induced by ultraviolet light. The guiding of a red laser beam with a full width at half-maximum of 15 mum is demonstrated. Buildup and decay times of the waveguide in pure KNbO(3) are of the order of 100 mus and 10 ms, respectively. The intensity of the guided light has no influence on the guiding properties over the range from 4 mW/cm(2) to 200 W/cm(2) . By reconfiguration of the waveguide, deflection angles of as much as 1.75 deg inside the crystal are achieved.

Submillisecond photorefractive response time of KNbO(3):Rb(+)

We investigate the photorefractive response time of diffraction gratings in Rb(+)-doped KNbO(3) crystals. Two components of charge carriers, with different response times, are found to contribute to the photoinduced index gratings. One component, which contributes to approximately 70% of the index grating, shows a submillisecond rise time when the total intensity of the writing beams is larger than 5 W/cm(2). The dependence of the response time on the light intensity and the grating wave vector is also investigated.