Porous Silicon Refractive Index Lattices

Abstract

Refractive index lattices with large contrast were fabricated by combining porous silicon with lateral patterning. The anodization of a p-substrate with periodically spaced n-doped regions produced a two-dimensional refractive index lattice comprised of low refractive index porous and high refractive index crystalline silicon regions. Under the lattice, the anodization proceeded not only downward but also sideways, extending a porous layer under the lattice. This porous layer acts as a bottom cladding layer to confine optical waves vertically. A higher refractive index contrast air–silicon lattice was fabricated by applying a selective etching or polishing mode anodization.