Effect of deuteration on the quadratic electrooptic properties of KDP

The isotopic effect on the magnitude of quadratic electrooptic coefficients in KDP is investigated. By employing both the Miller rule and assumption o f a rough constancy of intrinsic electrooptic coefficients, one can expect these quadratic electrooptic coefficients which are related to the electric field applied in the [100] direction, i.e. the coefficients g(1111), g(221 1) and g(3311) to be in DKDP almost twice larger than that for KDP. Our mea surements of the relative quadratic coefficient n(0)(3)g(1111)-n(e)(3)g(331 1) in DKDP are in contradiction with the prediction. We found g(1111), g(22 11) and g(3311) to be weakly dependent on the deuteration.