Thin film electro-optic modulator based on single crystal of N-(4-nitrophenyl)-(L)-prolinol (NPP) grown from melt by the modified Bridgman method

We discuss the plate-guiding method of growing micrometer-thick single crystal films of electro-optic organic material N-(4-nitrophenyl)-(L)-prolinol. This approach has the advantages of full control over the thickness of the film and selection of a proper seed for initial crystal growth. Characterization of the electro-optic properties of the films is performed using the intensity modulation technique with a low (of the order of 10 V) alternating driving voltage. Both the fundamental and double-frequency responses are used for the characterization. The electro-optic effect is pseudolongitudinal since the configuration of the experiment is that of a longitudinal intensity modulator. The main contribution to the effect originated from the transverse component of the external electric field. By purely electro-optic means we determine the orientation of the dielectric axes and measure the half-wave voltage, the figure of merit, and electro-optic coefficients r₁₂ and r₂₂ to be 3.24 kV and 99.2, 461, and 154 pm/V, respectively. We also find that electro-optic coefficients r₆₁ and r₆₃ are two orders of magnitude less than r₁₂ and r₂₂.