Photonic bandgap materials and birefringent layers based on anisotropically nanostructured silicon

Porous-silicon (PS) based multilayer periodic structures with photonic bandgaps (PBGs) and PS single layers that have a strong in-plane birefringence are produced by the electrochemical nanostructuring of crystalline silicon wafers of different crystallographic orientations. Calculations and experiments demonstrate the possibility of improving phase matching for second optical harmonic generation in PS-based PBG structures. Multilayer structures made of birefringent PS exhibit polarization-tunable (dichroic) PBGs, which offer much promise for various optical applications. Improved phase matching was experimentally demonstrated for second-harmonic generation in birefringent PS, suggesting that PBG and birefringent PS structures may serve to phase-match and enhance wave-mixing processes in nonlinear optical materials embedded in the pores of these matrices. (C) 2002 Optical Society of America.