Immunity of intersubband polaritons to inhomogeneous broadening

TL;DR

This study shows that intersubband polaritons are resistant to inhomogeneous broadening effects in multiple quantum well systems, maintaining narrow linewidths even at room temperature, which is promising for practical applications like polariton lasers.

Contribution

It demonstrates the robustness of intersubband polaritons against inhomogeneous broadening in MQWs, highlighting their potential for stable mid-infrared optoelectronic devices.

Findings

Polariton linewidths remain narrow despite broadening variations

Immunity to inhomogeneous broadening persists at room temperature

Coupling to a single photonic mode reduces effective linewidths

Abstract

We demonstrate that intersubband (ISB) polaritons are robust to inhomogeneous effects originating from the presence of multiple quantum wells (MQWs). In a series of samples that exhibit mid-infrared ISB absorption transitions with broadenings varying by a factor of 5 (from 4 meV to 20meV), we have observed polariton linewidths always lying in the 4 - 7 meV range only. We have experimentally verified the dominantly inhomogeneous origin of the broadening of the ISB transition, and that the linewidth reduction effect of the polariton modes persists up to room-temperature. This immunity to inhomogeneous broadening is a direct consequence of the coupling of the large number of ISB oscillators to a single photonic mode. It is a precious tool to gauge the natural linewidth of the ISB plasmon , that is otherwise masked in such MQWs system , and is also beneficial in view of perspective applications such as intersubband polariton lasers.