Subbandgap Asymmetric Surface Plasmon Waveguide Schottky Detectors on Silicon

Silicon-based surface-plasmon subbandgap detectors integrated with an asymmetric metal stripe are investigated for different metals, modes, and wavelengths of operation. Low-order bound modes supported by Al and Au stripes cladded below by silicon and covered by air are studied at the infrared wavelengths of 1310 and 1550 nm. Input optical power is end-fire coupled into the modes supported by the stripe, resulting in the total absorption of coupled power over a short length. The absorbed power creates excited carriers in the metal throughout the modal absorption volume, which can cross the Schottky barrier and become collected as photocurrent (internal photoemission). Measurements obtained for Au on n-type Si support predicted trends. The device has promise for applications in short-reach high-speed optical interconnects and silicon-based nanophotonics.