EFFECT OF ANGULAR CORRELATION ON NONLINEAR REFRACTIVE INDEX OF LIQUIDS

The effect of angular correlation (parallel orientation) between anisotropic molecules in liquids on the nonlinear refractive index has been studied both theoretically and experimentally. The theory predicts the reduction of the absolute values of the nonlinear index by several times 10% from those based on the simple orientational theory. The concentration (in isotropic or nearly isotropic molecules) and temperature dependences differ markedly from those based on the simple theory. A new theory taking into consideration this angular correlation agrees, at least qualitatively, with existing experimental data on self-focusing, and on optical and static Kerr effects, and with the present self-focusing experiment on mixed liquids. Also, it is shown that the Onsager theory of the local field, which may take into account molecular correlation in a certain way, gives a better agreement with experiments than Lorentz's theory. © 1968 The American Physical Society.