Second-harmonic generation in Ge-As-S glasses by electron beam irradiationand analysis of the poling mechanism

With the method of Maker fringe, second-harmonic generation (SHG) was obser ved in Ge-As-S glasses irradiated by electron beam. It is related to the sp ace-charge electrostatic field which makes the glasses poled and breaks the centrosymmetry of the glasses. So one new ministructure is formed and can keep constant for a long time, which makes the glasses difficult to restore relaxationally to its origin state and induces SHG. Second-order nonlinear ity chi ((2)) as high as 0.8 pmN was obtained. The results of thermally sti mulated depolarization current measurements indicated that the poled region s were located at the superficial layers of the glass surfaces (several mic rometers), which were the same as the calculated result in theory. The nonl inearities in Ge-As-S glasses are stable. (C) 2001 Elsevier Science B.V. Al l rights reserved.