Mid-Infrared intersubband polaritons in dispersive metal-insulator-metal resonators

TL;DR

This paper demonstrates room-temperature strong coupling of mid-infrared intersubband transitions with metal-insulator-metal resonators, enabling control over polaritonic dispersion and energy minima through surface patterning and post-processing.

Contribution

It introduces a method to engineer polaritonic dispersion and energy minima in mid-infrared resonators at room temperature, using surface patterning and post-processing techniques.

Findings

Achieved strong coupling at room temperature in the mid-infrared range.

Controlled the position of the polaritonic energy minimum via surface patterning.

Validated results with temporal coupled mode theory.

Abstract

We demonstrate room-temperature strong-coupling between a mid-infrared ($\lambda$=9.9 $\mu$m) intersubband transition and the fundamental cavity mode of a metal-insulator-metal resonator. Patterning of the resonator surface enables surface-coupling of the radiation and introduces an energy dispersion which can be probed with angle-resolved reflectivity. In particular, the polaritonic dispersion presents an accessible energy minimum at k=0 where - potentially - polaritons can accumulate. We also show that it is possible to maximize the coupling of photons into the polaritonic states and - simultaneously - to engineer the position of the minimum Rabi splitting at a desired value of the in-plane wavevector. This can be precisely accomplished via a simple post-processing technique. The results are confirmed using the temporal coupled mode theory formalism and their significance in the context of the concept of strong critical coupling is highlighted.