Competition Between Beam Fanning And Two-Beam Coupling In Barium Titanate

We have examined the time dependence of laser light for propagation parallel and antiparailel to the c-axis of a poled single crystal of barium titanate. A type of symmetric beam fanning was found to be more important in determining the transmission of our "best" crystal than two-beam coupling between the transmitted wave and that reflected from the back face of the crystal. This finding contradicts with previous reports of asymmetric transmission where effects of beam fanning were assumed small. Observation of the fanning motivated the more detailed measurements reported here.