Second-harmonic generation from porous silicon with a magnitude of two
orders greater than that from silicon crystalline wafers has been obs
erved. The measured effective second-order nonlinear susceptibility ch
i(ps.eff)(2) for a p-type porous silicon is 1.96 x 10(-7) esu which is
estimated on the base of a bulk property rather than on quantum confi
nement owing to its large surface to volume ratio.