Fig. 1: Quantum cascade region design and characterization.
From: Electronic transport driven by collective light-matter coupled states in a quantum device
a Schematic diagram of the detector active region. The quantum well on the left is highly-doped, and the optical excitation of the system is a many-body state, an intersubband plasmon, with an energy \({\widetilde{E}}_{12}=130{{{{{\rm{meV}}}}}}\) that is higher than the single particle-transition \({E}_{12}=108\) meV. The three quantum wells on the right constitute the extractor region for photogenerated electrons and are a single-particle system. b Absorption (blue line) and photocurrent (red line) measured respectively in a multipass configuration (d) and in a non-resonant cavity (mesa structure, e). The energies of the single-particle transition, E21, the collective state \({\widetilde{E}}_{12}\) and the extractor transition E31 are indicated by dashed lines. c The measurements in panel b are perfectly reproduced by our quantum model. The grey dotted line represents the photocurrent calculated with the conventional detector theory, i.e. \({G}_{H}(\hslash \omega )=1\) (see below). d Multipass configuration for the measurement of the absorption in the quantum well. e Mesa configuration for the measurement of photocurrent. In both cases the light couples in the sample through a facet polished at a 45° angle.
