Abstract

We have performed extensive experimental and theoretical studies of laser-induced second and third harmonic generation in crystalline, centrosymmetric metals, and semiconductors using 20-ps and 20-ns 1.06-μm pulses. In these materials second harmonic generation occurs because of surface electric dipole and bulk electric quadrupole/magnetic dipole sources. ¹ Third harmonic generation occurs because of bulk electric dipole sources. The high rank of the response tensors for these phenomena results in the harmonic radiation having an efficiency which varies periodically as a given sample surface [e.g., (100),(111)] is rotated about its normal. Such anisotropic behavior allows these nonlinear techniques to be used as probes of the bulk long range order (third harmonic) and surface structure (second harmonic). Examples of data are presented from crystalline silicon and aluminum and ion-implanted silicon. A simple theoretical model for the anisotropic part of the nonlinear response is given in terms of material parameters.

© 1985 Optical Society of America