Absolute Measurement of an Optical-Rectification Coefficient in Ammonium Dihydrogen Phosphate

A direct measurement of an optical-rectification coefficient in ammonium dihydrogen phosphate (NH₄{H}₂P{O}₄$) is described. The result is $({{X}⁰}xyz+{{X}⁰}xzy=(1.32±{}0.18)×{}{10}^{{-}7}$ esu, at 6943 {} and 27^∘{}C. The 15% uncertainty represents an improvement by a factor of 20 over the previous absolute measurement of an optical rectification coefficient by Bass et al. The improved precision makes possible a more meaningful test of a theoretical relationship between the optical-rectification coefficients X⁰, and the linear electro-optic coefficient X^ω. This relationship, first pointed out by Armstrong et al. and studied in more detail by Ward and Franken, is (X⁰ᵢⱼₖ+X⁰ᵢₖⱼ)=1/4(X^ωⱼᵢₖ+X^ωₖᵢⱼ). It is concluded that the present measurement, together with electro-optic data from the literature, is consistent with the validity of this relationship.