CONTRADIRECTIONAL 2-BEAM COUPLING IN ABSORPTIVE PHOTOREFRACTIVE MATERIALS - APPLICATION TO RH-DOPED STRONTIUM BARIUM NIOBATE (SBN-60)

Contradirectional two-beam-coupling gains are measured in Rh-doped str ontium barium niobate (SBN) as a function of the Rh concentration and the incident pump-probe beam ratio. These measurements indicate that l arger two-beam-coupling coefficients in this contradirectional geometr y (as large as similar to 16 cm(-1)) are typically linked to stronger optical absorption in the more heavily doped samples. The effects of s uch strong absorption are explicitly included in a theoretical analysi s applied to the measured data. In particular, earlier theoretical tre atments of this two-beam-coupling process with nonnegligible absorptio n are extended to yield an approximate expression for the probe gain. The accuracy of this analytic expression is then verified by compariso n with exact numerical results as well as with experimental measuremen ts in the Rh-doped SBN samples. Further experimental and theoretical c omparisons are made after the contradirectional two-beam-coupling proc ess is related to asymmetric transmission through a photorefractive wi ndow (i.e., one-way glass), again in the presence of strong absorption .