Can Optical Second Harmonic Generation be Used as a Surface Probe for Non-centrosymmetric Media

In recent years, optical second harmonic generation (SHG) has proven to be a very effective and sensitive tool for studies of a large variety of surface and interface properties (1). However, experiments so far have been restricted to substrates with inversion symmetry. This is because in centrosymmetric media, SHG is forbidden in the bulk but allowed at the surface, giving the technique its unique surface specificity.