Elliptical silicon nanowire photodetectors for polarization-resolved imaging.

Polarization-resolved imaging offers many advantages over conventional imaging because it provides additional information on materials and scenes. In this study, we present an image sensor pixel for polarization-resolved imaging based on an all-silicon nanowire device. As the structure has an intrinsically polarization-dependent response, it is not necessary to employ a polarizer. We fabricate pixels consisting of etched vertical silicon nanowires with elliptical cross-sections that incorporate vertical p-i-n junctions. Our photocurrent measurement reveals that the spectral responsivities are dependent on the polarization state of incident light. Polarization-resolved imaging is performed with fabricated devices. This approach is different from conventional approaches using polarization filters because absorbed light in the elliptical nanowire is converted to photocurrent while light absorbed by a polarization filter is discarded.