Intersubband Resonance Fluorescence

In 1969 Mollow predicted that when a two-level quantum system is strongly pumped at resonance, it reemits light not only at its resonance frequency but also at two satellite frequencies. This result of quantum optics theory has been tested in many solid-state systems that can be described as two-level systems. We show that three peaks appear also when a two-dimensional electron gas confined in a quantum well is continuously pumped between two conduction subbands. Describing the resonance fluorescence with a many-body theory, we could go beyond the usual independent-dipole approximation. Remarkably, coherence in the electron gas can lead to a modified fluorescence spectrum. Moreover, with asymmetric quantum wells it is possible to engineer otherwise forbidden transitions, leading to a new tunable emission line, in the terahertz range.

BR Mollow, Phys Rev 188, 1969 (1969).
NS, CC Phillips and S De Liberato, Phys Rev B 89, 235309 (2014).