Charge-sensitive infrared phototransistors with integrated plasmonic photocouplers

Abstract

A plasmonic coupler, which consists of periodic metal gratings and a tapered waveguide, is integrated to a charge-sensitive infrared phototransistor (CSIP) for 45 µm wavelength radiation. The period and height of the gratings are about 42 µm and 4 µm, respectively. The gratings convert normally incident radiation into a surface wave, which is converged to the active region of the CSIP through the tapered waveguide. Both rise rate and signal amplitude become larger, due to the presence of the plasmonic coupler.