Abstract

Optical second harmonic generation (SHG) is forbidden in the bulk of centrosymmetric media but necessarily allowed at the surface. The process has been used as a versatile tool for surface studies on a wide variety of interfaces. It is rather sensitive, capable of detecting submonolayers of molecules on surfaces with relatively low laser powers.¹ Normally, pulsed laser systems are used as the pump source. It can be shown, however, that the maximum surface SH signal generated by a cw laser from most materials, assuming that the incident intensity is limited by thermal damage, may be larger or comparable with that generated by a typical pulsed laser, if the beam area is <10⁻⁵ cm². With focusing, surface SHG can have a spatial resolution limited in principle by the optical wavelength. Thus it is ideally suited for surface optical microscopy.

© 1986 Optical Society of America