Fourier-transform sum-frequency surface vibrational spectroscopy with femtosecond pulses

Summary form only given. Infrared-visible sum-frequency generation (SFG) has been proven to be a powerful probe for vibrational spectroscopic investigation of surfaces and interfaces. It is highly surface specific and has a submonolayer sensitivity. As a nonlinear optical process, SFG puts a premium on high input beam intensities. One would therefore like to employ input pulses as short as possible. However at subpicosecond pulse widths, the bandwidth of pulses would already exceed the widths of many vibrational resonances of interest. By combining SFG with a Fourier transform (FT) interferometric technique we can overcome this difficulty. Using 100-fs input pulses in our SFG surface monolayer vibrational spectroscopy studies, we have obtained a spectral resolution determined only by the maximum optical path difference between the two arms of an interferometer, as is common for FT spectroscopy.