Direct polariton-to-electron tunneling in quantum cascade detectors operating in the strong light-matter coupling regime

TL;DR

This paper reports the experimental realization of mid-infrared quantum cascade detectors operating in the strong light-matter coupling regime, revealing that polaritonic states enable resonant tunneling for efficient photo-current extraction.

Contribution

It introduces a refined semi-classical coupled modes model to accurately describe polaritonic features in QCDs and identifies polariton-to-electron tunneling as the main mechanism.

Findings

Strong light-matter coupling observed at 10 μm wavelength

Refined model accurately reproduces optical and electrical spectra

Resonant tunneling from polaritonic states dominates photo-current extraction

Abstract

We demonstrate mid-infrared quantum cascade detectors (QCD) operating in the strong light-matter coupling regime. They operate around $\lambda = 10~\mu m$ with a minimum Rabi splitting of 9.3 meV. A simple model based on the usual description of transport in QCDs does not reproduce the polaritonic features in the photo-current spectra. On the contrary, a more refined approach, based on the semi-classical coupled modes theory, is capable to reproduce both optical and electrical spectra with excellent agreement. By correlating absorption/photo-response with the simulations, we demonstrate that - in this system - resonant tunneling from the polaritonic states is the main extraction mechanism. The dark intersubband states are not involved in the process, contrary to what happens in electrically injected polaritonic emitters.