THE ROLE OF LEAD COMPONENT IN 2ND-HARMONIC GENERATION IN LEAD SILICA BY ELECTRON-BEAM IRRADIATION

It is found that the second-order nonlinearity induced in lead silica by electron-beam irradiation increases linearly with the lead percenta ge of the glass and a value of 4 pm/V has been estimated for ZF(7) lea d silica. The electrostatic field created under the glass surface incr eases with the lead percentage, which can be explained by the theory o f stopping collisions of fast electrons. The layer depth is found prop ortional to the inverse square root of the lead percentage. The accumu lative effect of electron irradiation for inducing the nonlinearity ap pears limited by the breakdown threshold in the charged layer. An opti mum total electron charge per unit of scanned area of 0.29 C/m(2) has been determined for SF2 glass. Nonlinearity layer depths of 1.9-4.1 mu m have been estimated by chemical etching for different lead silica a nd electron voltages, and the coefficients of the Bohr-Bethe penetrati on formula have been determined for SF2 glass. (C) 1998 American Insti tute of Physics. [S0003-6951(98)04047-9].