Surface nonlinear optical spectroscopic studies of polymers

As a second-order nonlinear optical process, sum-frequency generation (SFG) is forbidden in media with inversion symmetry but allowed at surfaces or interfaces. It can therefore be used effectively as a surface probe. Scanning the infrared input over surface vibrational resonance yields a surface vibrational spectrum. Analysis of the spectra obtained with different input/output polarization combinations provides information about orientations of the different molecular groups at the surface.