DISPERSION AND BAND-GAP SCALING OF THE ELECTRONIC KERR EFFECT IN SOLIDS ASSOCIATED WITH 2-PHOTON ABSORPTION

Measurements of the nonlinear refractive index of several semiconductors using beam-distortion methods and four-wave mixing show a strong systematic dispersion in the bound-electronic nonlinearity (electronic Kerr effect n2) near the two-photon-absorption edge. This eventually turns from positive to negative at higher frequencies. We find that by using the two-photon-absorption spectrum as predicted by a two-parabolic-band model, we can predict the observed universal dispersion, scaling, and values of n2 that range over 4 orders of magnitude and change sign, using a simple Kramers-Kronig analysis (i.e., relating the real and imaginary parts of the third-order susceptibility). The resulting scaling rule correctly predicts the value of n2 for all the 26 different materials we have examined. This includes wide-gap dielectrics which have 3 to 4 orders of magnitude smaller values of n2 than semiconductors. © 1990 The American Physical Society.