A Powerful Nonlinear Optical Technique to Characterize Surfaces and Interfaces Sum Frequency Generation Vibrational Spectroscopy

In the last two decades, a nonlinear optical technique - sum frequency generation (SFG) vibrational spectroscopy was developed into a powerful characterization method to probe the molecular structures of various surfaces and interfaces in situ . In this paper, we gave a general introduction of the SFG theory and two case studies to demonstrate the power of the SFG spectroscopy.