Multispectral infrared detection using plasmon-assisted cavities

Abstract

We report the demonstration of multi-spectral quantum dots-in-a-well infrared photo-detectors through the coupling of incident light to resonant modes of surface plasmons. The integration of a surface plasmon assisted cavity with the detector results in shifting the peak wavelength of absorption of the detector to that of the resonant wavelength of the cavity. The cavity consists of a square lattice structure with square holes in it. A wavelength tuning of 8.5 to 9 μm was observed, by changing the pitch of the fabricated pattern forming the cavity. Polarization sensitive detectors can be fabricated by breaking the symmetry of the lattice. This is achieved by stretching the lattice constants along the x and y directions. A DWELL detector with resonant frequency at 6.8 μm where the response of the 0 ° polarization is twice as strong as the 90° polarization is reported. This technique, in principle, is detector agnostic and shows promise in fabrication of multi-spectral focal plane arrays (FPA).