Correlation between the nonlinear optical constants and the structural relaxation parameters in chalcogenide glasses

It is well known that chalcogenide glasses exhibit high values of nonlinear optical constants in addition to the widely studied photostructural changes. However, the relations between these properties are not sufficiently understood. On the other hand, according to the bond strength-coordination number fluctuation (BSCNF) model proposed by one of the authors, the viscous behavior is described in terms of the average bond strength, coordination number, and their fluctuations of the structural units that form the system. In the present study, the interrelation between the nonlinear optical constants and the structural relaxation parameters defined from the BSCNF model has been investigated for the case of chalcogenide systems. It is found that the third order nonlinear optical susceptibility increases with the fluctuations of the structural relaxation parameters. The correlation found is discussed based on the BSCNF model and the average electronegativity.