Nonlinear refractive index in thin Ge/sub x/Sb/sub 40-x/S/sub 60/ films

Abstract

A suitable relationship between the linear n/sub L/ and the nonlinear refractive index n/sub 2/ has been used for prediction of the nonlinear behavior of the refractive index in thin Ge/sub x/Sb/sub 40-x/S/sub 60/ films. The parameters (linear refractive index n/sub L/ and the dispersion parameters E/sub 0/ and E/sub d/) necessary for the calculation of the n/sub 2/ are studied by means of spectrophotometry in the light wavelength region of 0.5-2.5 /spl mu/m. It has been established that the nonlinear refractive index increases with increasing linear refractive index. The obtained results for n/sub L/ and n/sub 2/ are considered in terms of the average coordination number Z. The observed peculiarity in the compositional dependences of the linear and nonlinear refractive indices around Z=2.65-2.67 can be connected with the structural changes associated with a topological phase transition of the film structure.