Nanosecond optical response to pulsed uv excitation in KNbO3

Grating formation in pure KNbO3 crystals is observed after short pulse uv illumination which allows interband photoexcitation. The time resolved diffraction of 70 ps pulses at 532 nm on a nanosecond time scale is measured in geometries where an electro-optic contribution is significant and in geometries where it is forbidden by crystal symmetry. Diffraction efficiencies up to 10(-3) that build up in less than 0.1 ns, followed by a build up during 1 ns to efficiencies up to 3 x 10(-3) are observed. (C) 1997 Elsevier Science B.V.