Nonlinear refraction anisotropy of CdS crystals near the fundamental absorption edge

A method for determining the nonlinear coefficients of the refractive index of dissipative media was developed. It was used to find the refraction nonlinearity of wide-gap CdS semiconductors near the fundamental absorption edge along various crystallographic directions. It was observed that a CdS crystal has a high nonlinear susceptibility χ⁽³⁾ near a one-photon resonance. The nature of the observed anisotropy is discussed.