OPTICAL, NONLINEAR-OPTICAL, AND ELECTROOPTICAL PROPERTIES OF 4'-NITROBENZYLIDENE-3-ACETAMINO-4-METHOXYANILINE (MNBA) CRYSTALS

Optical, nonlinear optical, and electrooptical pg-properties of 4'-nit robenzylidene-3-acetamino-4-methoxyaniline (MNBA) single crystals have been investigated. The refractive indices were determined in the wave length range of 514 to 1064 nm using an interferometric method. The el ectrooptical coefficients r11, r13, r31, and r33 were measured using a phase modulation technique. The dispersion of the largest electroopti cal coefficient, r11 (= 29 pm/V at lambda = 633 nm), was seen to follo w the theoretical two-level model. Using the standard Maker fringe tec hnique, we determined the nonlinear optical susceptibilities. The larg est coefficient was found to be d11 = 175 pm/V at lambda = 1064 nm. El ectric-field-induced second-harmonic generation was used for the deter mination of the molecular second-order nonlinear optical susceptibilit y yielding a good quantitative agreement when compared with the larges t nonlinear optical and electrooptical coefficients in the framework o f the molecular gas model with charge transfer along the polar molecul ar axis. Electroabsorption measurements near the band edge were perfor med that allowed us to calculate the field-induced frequency shift of the dominant oscillator. This field-induced frequency shift is of the same order of magnitude as the frequency shift calculated from the ele ctric-field-induced changes of the refractive indices (electrooptical effect).