Electric-field frequency dependence of Pockels coefficients in 2-amino-5-nitropyridium dihydrogen phosphate organic–inorganic crystals

The electro-optic and dielectric properties of organic–inorganic 2-amino-5-nitropyridium dihydrogen phosphate crystals were measured near room temperature at a wavelength of 632.8 nm and as a function of an electric-field frequency that varied from 1 kHz to 40 MHz. The frequency dispersion of the electro-optic coefficients and their comparison with the second-harmonic generation coefficients showed that the largest part of the electro-optic properties is electronic in origin (whereas the piezo-optic contribution is small). Results reveal a large anisotropy of the ionic and electronic contributions that is related to the contributions of the organic molecule to nonlinear polarizability.