Optical responses from a polycrystalline copper electrode under pulsed infrared laser irradiation

Abstract

The study of optical second harmonic generation (SHG) of a polycrystalline copper electrode in the course of its anodic dissolution in aqueous electrolytes has shown two different types of SHG signal. The first type is observed in H₂SO₄ solutions, pH 1 and is caused by molecular adsorption of the electrolyte species on the electrode. The Second type is observed in potassium halide electrolytes and is caused by surface copper(I) halide layers formation under anodic potential bias. These types of SHG signal differ in intensity, dependence on excitation power and cyclic reproducibility. A strong non-monochromatic background optical signal was detected in alkaline solutions. The study of the precise nature of this signal indicates that it originates from anodic formation of a thin film of surface copper oxides and a repetitive thermoshock destruction of this film under IR laser pulses.