EKSPLA Picosecond Vibrational Sum Frequency Generation (SFG) Spectrometer
A fixed visible pump laser beam and a tunable IR laser beam are overlapped at the interface and light with the sum frequency of the two fundamental beams is generated. As the IR laser light is scanned over the spectral range of interest, SFG active vibrational modes of molecules at the interface give resonant contributions to the SFG signal. This resonant enhancement provides detailed spectral information about interfacial species. SFG is a second-order nonlinear process, which is forbidden in isotropic or inversion symmetric media. At surfaces or interfaces any isotropy or inversion symmetry is necessarily broken, which makes SFG highly surface specific.