Anisotropic Second Harmonic Generation Induced in Silicon and Germanium by Picosecond and Nanosecond Laser Pulses

ABSTRACTWe have performed experimental and theoretical studies of the origins of anisotropic second harmonic generation observed in reflection from (111) and (100) faces of crystal Ge and Si. Results, using 25 psec and 20 nsec 1.06 and 0.53 μm pump beams allow us to conclude that induced plasmas have no role in the effect and that the mechanism for the nonlinearity is associated with quiescent surface dipolar or bulk quadrupolar effects. Dispersion in the anisotropic behaviour is presented and the application of anisotropic harmonic generation to structural determinations of Si and Ge during laser annealing will be discussed.