Phase matching of second-harmonic generation in birefringent porous silicon

Optical second-harmonic generation is investigated in free-standing (110) p orous silicon films having strong inplane birefringence. Based on the measu red values of the refractive indices, the conditions of phase matching are calculated and verified in the experiments on angular and polarization depe ndences of second-harmonic generation. Filling pores with a transparent die lectric liquid allows phase matching to be achieved and the second-harmonic signal to be increased by two orders of magnitude. The results of these ex periments suggest an opportunity to form new-type nonlinear-optical media c onsisting of birefringent porous silicon as a phase-matching matrix for the materials embedded in the pores.