DC-ELECTRIC-FIELD-INDUCED OPTICAL 2ND-HARMONIC GENERATION AT THE SMOOTH METAL-ELECTROLYTE INTERFACE

The reflected second harmonic (SH) intensity is established to be a quadratic function of voltage applied to the smooth silver-electrolyte interface in a wide range of angles of incidence of the fundamental radiation. The nonlinear reduction problem is solved to recapture the voltage dependence of Rudnick-Stern's parameter alpha(phi) that turns out to be linear in the range from -0.5 to -1.2 V (versus saturated Ag-AgCl electrode). In this range, the electro-induced nonlinearity of conduction electrons is the predominant mechanism behind the electric-field-induced SH. The deviations from linear dependence of alpha(phi) are associated with the specific adsorption of anions.