Planar silicon-based light polarizers.

Silicon-based thin-film polarizers operating in the visible and near-infraed spectral range are fabricated by electrochemical etching of bulk silicon wafers. Anisotropically etched (110) porous silicon layers exhibit a strong in-plane anisotropy of the refractive index. Stackes of alternating layers with different mean refractive indices and thicknesses act as dichroic Bragg reflectors or microcavities, respectively. Both structures have two distinct reflection and transmission bands depending on the polarization of the incident linearly polarized light. Planar polarizers are realized through the combination, in one structure, of a dichroic reflector with either a second reflector or a microcavity with different spectral responses.