The role of lead component in second-harmonic generation in lead silica by electron-beam irradiation

Abstract

It is found that the second-order nonlinearity induced in lead silica by electron-beam irradiation increases linearly with the lead percentage of the glass and a value of 4 pm/V has been estimated for ZF7 lead silica. The electrostatic field created under the glass surface increases with the lead percentage, which can be explained by the theory of stopping collisions of fast electrons. The layer depth is found proportional to the inverse square root of the lead percentage. The accumulative effect of electron irradiation for inducing the nonlinearity appears limited by the breakdown threshold in the charged layer. An optimum total electron charge per unit of scanned area of 0.29 C/m2 has been determined for SF2 glass. Nonlinearity layer depths of 1.9-4.1 μm have been estimated by chemical etching for different lead silica and electron voltages, and the coefficients of the Bohr-Bethe penetration formula have been determined for SF2 glass.