Design of Plasmonic Perfect Absorbers for Quantum-well Infrared Photodetection

Based on analytic formulas and numerical simu- lations, we propose a plasmonic cavity with a top Au grating and bottom Au film to enhance quantum-well infrared pho- todetectors (QWIPs) operating at wavelengths between 2 and 30 μm. By using plasmonic cavity modes, QWIPs can detect light even at normal incidence. With using optimal structural parameters, light can be almost perfectly absorbed by the cavity and over 54 % of the light is absorbed by the QW active region. Compared with the reference structure (without Au layers and with an isotropic active region), the absorption enhancement is over 30 times in the QW active region at normal incidence and remains high value (> 4.5) for p -polarized light in a broad range of incident angle (|θ| < 60 0 ).