Influence of off-axis-light on depolarization loss of electrooptical crystal

The relation between the angle of off-axis-light and the depolarization loss has been calculated under different incidence of polarization. The results show when the thickness of crystal was settled, the depolarization loss is directly proportional to the angle of off-axis-light and the angle between the polarization of laser beam and the main axis of crystal in some confine. When the thickness of crystal is 10mm, the depolarization loss under different case was measured. When the angle of off-axis-light is less than 15mrad, the depolarization loss of electro-optical crystal is less than 0.5%, but when the angle is larger than 15mrad, the depolarization increases very quickly. The measurement results are in accord with ones of the calculation.