The nonlinear optical response of semiconductor interfaces using three
-wave mixing experiments in general, and second harmonic generation (S
HG) in particular, has been widely studied, but it is only recently, w
ith the advent of commercial tunable pulsed laser sources, that the sp
ectroscopic aspect of SHG can be more readily exploited. Results from
porous Si and Si(100)-Sb are reported that illustrate the potential of
spectroscopic SHG as a probe of semiconductor interfaces.