Semiempirical relation between non-linear susceptibility (refractive index), linear refractive index and optical gap and its application to amorphous chalcogenides

Using generalized Miller's rule and linear refractive index (n), simple relation is suggested for estimation of the non-linear susceptibility (chi((3))) and non-linear refractive index (n(2)). This relation provides reasonable agreement between the calculated and experimental chi((3)), n(2) values for more than 90 glassy oxides (chi((3))) and also for 22 optical crystals (n(2)). Prediction of chi((3)) and n(2) values for chalcogenide glasses indicates that non-linear susceptibility can reach up to chi((3)) congruent to 2x10(-10) esu for some telluride glasses, Simple semiempirical correlation between n(2) and the optical gap is suggested.