Terahertz lasing from intersubband polariton-polariton scattering in asymmetric quantum wells

TL;DR

This paper demonstrates that asymmetric quantum wells enable dipolar transitions between intersubband polariton branches, allowing for efficient, tunable terahertz lasing, which was forbidden in symmetric systems.

Contribution

The study introduces a quantum field theory showing how asymmetry in quantum wells permits terahertz lasing via interbranch polariton transitions.

Findings

Allowed dipolar transitions in asymmetric wells enable terahertz emission.

Predicted high-efficiency, tunable terahertz lasing.

Quantum field theory models the system's behavior.

Abstract

Electric dipole transitions between different cavity polariton branches or between dressed atomic states with the same excitation number are strictly forbidden in centro-symmetric systems. For doped quantum wells in semiconductor microcavities, the strong coupling between an intersubband transition in the conduction band and a cavity mode produces two branches of intersubband cavity polaritons, whose normal-mode energy splitting is tunable and can be in the terahertz region. Here, we show that, by using asymmetric quantum wells, it is possible to have allowed dipolar transitions between different polaritonic branches, leading to the emission of terahertz photons. We present a quantum field theory for such a system and predict that high-efficiency, widely tunable terahertz lasing can be obtained.