Dispersion of the Electro-Optic Kerr Effect in the Infrared Region

The infrared dispersion of electro-optic anisotropy has been investigated theoretically and experimentally. Anomalies of the refractive index in the neighborhood of resonant absorptions are accompanied by anomalous dispersion in the electro-optic Kerr effect. A theoretical analysis of the effect of molecular structure on the form of the anomalous behavior demonstrates that the relative orientation of the permanent molecular dipole and the radiation-induced dipole determines the sign of the deviation of the dispersive behavior from normal. The dependence on the applied electrostatic field strength is predicted to be the same in resonant and nonresonant regions. Experimental examination of the electro-optic anisotropy of nitrobenzene at field strengths of 28 000 v/cm to 48 000 v/cm in the overtone region (1.5–5.6 μ) of the infrared spectrum confirms these theoretical conclusions.