Photorefractive effects in tantalum-doped potassium niobate

Photorefractive gain is measured in poled 1% tantalum-doped potassium niobate (KNbO(3)). Two-wave mixing experiments are presented which exploit the r(42) coefficient of KNbO(3) by employing nonsymmetric geometries which rotate the grating vector away from the optic axis. The effect of this rotation on the exponential gain coefficient is shown. Experimental results are compared to an analytic expression derived for this parameter. The experiments were performed using an argon laser stabilized at lambda = 514.5 nm. The light was extraordinarily polarized, and the beams were incident on the b-face of the crystal. The absorption and the response time of the crystal were measured. Losses due to scattering and phase conjugation were also investigated.