Photorefractive effect in LiNbO3 directional couplers.

Experimental results on the photorefractive effect in Ti-indiffused LiNbO3 directional couplers at GaAs and He-Ne wavelengths are presented. The photorefractive effect has been observed as drift in the switching state of this device at GaAs wavelengths (0.81 and 0.85 microm) for intensities (powers) as low as 32 W/cm2 (3.2 microW). Analysis of this effect indicates refractive-index changes as large as 8 x 10(-4) may be occurring. Measurements also suggest the possibility of two time constants in the relaxation of the photorefractive effect in these devices.