Strength and symmetry of the third-order nonlinearity during poling of glass waveguides

Negative thermal poling introduces second-order nonlinear effects into silica glass. The effects are studied using the charge separation model allowing for the third-order nonlinear effect to be anisotropic. The second-order nonlinear coefficient /spl chi//sup (2)/ is found to be consistent with the results reported previously by Arentoft et al. (1999), Ren et al. (2002), and Marckmann et al. (2001) and the third-order nonlinear coefficient /spl chi//sup (3)/ is found to be anisotropic but constant during poling.