Abstract

Infrared-visible sum-frequency generation (SFG) has become a widely applied tool for the study of molecular monolayers and interfaces between molecular fluids.¹ It combines the interface selectivity of a second-order nonlinear optical process with the specificity of a spectroscopic technique. A particularly attractive feature of IR-visible SFG is that by scanning the IR wavelength over the vibrational modes of the molecule one can independently probe its various subunits. In this way, one can gain information on the molecular conformation on the interface and, in specific cases, on the spatial orientation of the subunits. The full power of this method has so far not been employed because with most available coherent infrared sources, one can only cover part of the vibrational spectrum of many molecules.

© 1996 Optical Society of America