Extraordinary plasmon-QD interaction for enhanced infrared absorption

Abstract

The use of metallic nanostructures for enhanced transmission and near field phenomena have been a topic of extensive research. Here we present integration of active media, consisting of InAs quantum dots (QD) embedded in quantum wells, with 2 dimensional metallic hole arrays (2DHA) leading to a strong interaction between resonant surface plasmons, excited at the metal-semiconductor interface, and intersubband transitions of quantum dots. The presence of a low-loss absorber within the enhanced near field region of 2DHA leads to an enhancement of photoresponse. The parameters of 2DHA were designed to overlap with absorption peaks of QDs. We present techniques of fabrication, accurate characterization of enhancement and efforts to optimize the 2DHA-QD coupling. Over an order of magnitude enhancement in photoresponse is observed due to spectral matching of intersubband absorption of quantum dots to that of 2DHA resonance, optimal placement of QD within the structure, and improved interaction lengths due to lateral propagation. This enhancement is also accompanied by significant narrowing of linewidth and the ability to tune the resonance by varying the 2DHA parameters. A hexagonal lattice with periodic circular holes on a thin gold film is used as the 2DHA. With further optimizations, these structures have significant applications in the mid-wave infrared (3-5 µm) and long-wave infrared (8-12 µm) regions for multispectral and polarization sensitive sensing.

Controlling quantum-dot light absorption and emission by a surface-plasmon field

“…Our results clearly demonstrate the ability to control probe-field optical gain and absorption switching and photon conversion by a surface-plasmon field with temperature-driven frequency detuning in such a nonlinear system led by dressed electron states, very similar to the 'gate' control in an optical transistor. These conclusions should be experimentally observable [27,28]. On the other hand, our numerical results also provide an example for demonstrating the so-called quantum plasmonics, [29] where the nature of surface-plasmon polaritons and the nature of quantum-confined electrons are hybridized through near-field coupling.…”