Light intensity dependence of the refractive index of non-dissipative media by a semi-macroscopic approach

By a semi-macroscopic method the following equation is derived n 2 στ - n 2 0 δ στ = (( n 2 0 + 2)/3){ AI δ στ + B (3 I στ - I δ στ defining the change in optical permittivity tensor n 2 στ due to strong light of intensity I . The quantity A describes isotropic changes in n στ related with linear and non-linear polarization and opticostriction, whereas B accounts for the optical anisotropy induced in the medium by an intense (e g. laser) beam. The optical birefringence constant B is discussed in detail statistically for the case of multicomponent systems of interacting molecules; it is evaluated numerically for several liquids and compared with the experimental data - the third-order polarizabilities of their molecules are found to be of the order of 10 -36 e s.u.