Corrugated plasmonic cavity for enhanced intersubband photodetection

We study the optical properties of a corrugated plasmonic cavity consisting of a perforated metal film and a flat metal sheet separated by a semiconductor spacer. Corrugation enhances dramatically the coupling between the propagating surface plasmon and the Fabry-Perot mode and induces Rabi-like splitting forming bright bonding and dark anti-bonding modes. The anti-bonding mode exhibits considerably higher volume-averaged field enhancement factors (∼16.5 for E-field and ∼14.1 for E_z-component) than its bonding counterpart as well as a very high polarization conversion ratio (∼85.5%) from transverse electric to transverse magnetic waves. These characteristics make the corrugation induced anti-bonding mode particularly suitable for semiconductor quantum well intersubband photodetectors. Our work may provide a general guideline to the design of metamaterial-coupled intersubband hybrid devices for practical applications.