Photorefractive properties of cobalt-doped strontium barium niobate crystals

The two-wave interaction (at λ = 488 nm) in strontium barium niobate crystals doped with cobalt ions (Co:SBN) was studied. The experimental dependences of the gain coefficient on the grating period and of the grating response time on the writing beam intensity were used to calculate the Debye screening length, the diffusion length, the dark conductivity, and the effective concentration of carrier traps for a series of Co:SBN crystals with different dopant concentrations. The crystals were shown to have high coupling coefficients (Γ = 33 cm-1) and short optical response times (τ = 140 ms for I = 1 W cm-2 ). This, in combination with a high photorefractive sensitivity (S = 39 cm2 J-1 ), determines the efficiency of their use in the storage of optical information and in laser phase conjugation. (nonlinear optical phenomena)