Wavelength-selective waveguide photodetectors in silicon-on-insulator

We show that silicon-on-insulator substrates, combined with a low index waveguide, can yield intrinsically wavelength-selective devices for multiwavelength applications. We demonstrate a simple wavelength-selective photodetector that resembles an asymmetric directional coupler with a polymer waveguide coupled to a silicon waveguide. Only certain wavelengths are phase-matched between the two guides and transfer from the polymer to the silicon. Operating the device at the band edge of silicon, the coupled radiation is absorbed and generates photocurrent. The 400 μm long detector exhibits a linewidth of a few nm, limited by the uniformity of the silicon-on-insulator material.