Nonlinear optical spectroscopy of solid interfaces

Nonlinear optical spectroscopies for the investigation of solid surfaces and interfaces are reviewed. Emphasis is on the surface-specific second-order nonlinear optical response. Following a brief introduction on the fundamental, a broad variety of applications of second-harmonic (SHG) and sum-frequency (SFG) spectroscopic techniques are discussed. An outlook on exciting new opportunities provided by these techniques is presented.