Transport-Induced-Grating Interferometry;Application to Photorefractive Bi sub 12 Tio sub 20,
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
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We have developed a technique to measure interferometrically charge-transport-induced refractive index gratings in photoconductive insulators. All four parameters needed to describe fully the interaction between the two beams Bragg matched to the grating can be determined. We use the method to find that the complex optical polarizability of an occupied charge trap equals that of an unoccupied trap plus 0.7 - i4.5 or - 0.7 or - iO.4 x 10 to the -22nd cu.cm. in photorefractive Bi12TiO20. A spatially sinusoidal grating of optical intensity can produce a sinusoidal grating of occupied deep traps in photorefractive crystals. Under a wide variety of experimental conditions, a steady trap grating is produced, after sufficiently long times, that results in a change delta epsilon of the optical dielectric tensor of the form.
- Electricity and Magnetism