PHOTOREFRACTIVE PROPERTIES OF BI4TI3O12

Three gratings are observed during holographic recording in Bi4Ti3O12: There is a primary photoinduced grating with fast response and a deph asing of pi/2 with respect to the light pattern. It is compensated for by a complementary charge grating with much slower response. The thir d grating identified by phase-shift-experiments is an absorption grati ng. At an intensity of about 0.5 W/cm(2), apeak refractive-index chang e of Delta n = 1.8 X 10(-5) is achieved with a response time constant tau(1) = 40 ms. The mobility-lifetime product of the charges responsib le for the primary grating is mu tau(R1) = 7.0 X 10(-12) cm(2)/V. The conductivity of the complementary charges is much smaller than that of the primary charges, which makes it possible to prolong the readout t ime of the recorded holographic grating considerably.