Evolution of linear electro-optic coefficients and third-order nonlinearity during prolonged negative thermal poling of silica fibre

Evolution of the linear electro-optic coefficients in the prolonged negative thermal poling of germanosilicate fibre reveals movement of charge distributions in the fibre. As previously reported, the third-order nonlinearity of the fibre core increases by ∼1.8. However, for the first time this value is observed to be fairly constant during the poling process.