Abstract

In the electric dipole approximation, an intense laser beam incident on a centrosymmetric material will not generate any even ordered harmonics. In particular, there will be no second harmonic response generated by the bulk of the material. At the surface of a centrosymmetric medium, the inversion symmetry is broken, allowing for a second order response characterized by the second order nonlinear susceptibility, χ^{(2) 1}. Thus, χ⁽²⁾ has an inherent surface sensitivity which we utilize in order to image surfaces, interfaces, and thin films.

© 1996 Optical Society of America