<title>Study on the surface currents density with second-harmonic generation from silver</title>

Abstract

Quantitative measurements of reflected optical second harmonic generation (SHG) versus the angle of polarization of the incident light from the interface between opaque silver films and several glasses are presented. And we also measured the reflected SHG from the surface of vacuum cold-evaporated thick silver film on a polycrystalline silver substrate in ultra-high vacuum (UHV) chamber before and after annealing the specimen. For comparison, the reflected SHG from 99.99% finely polished polycrystalline silver surface was detected in UHV. By calibrating the reflected SHG from the silver film to the transmitted SHG from a z- cut quartz, the value of normal current parameter a could be determined. We measured that the phenomenological normal current parameter a had a value of 2.1 for glass-silver interface and -9 for polycrystalline silver sample. And that a varied from 7 to -5 for the cold-evaporated silver film on a polycrystalline silver substrate with the sample annealed. The experimental result shows that the SHG signal is sensitive to the surface structure of the silver film. The electro-dynamic theory is used to fit the experimental results.