Strong Light–Matter Interaction and Spontaneous Emission Reshaping via Pseudo-Cavity Modes

Abstract

Strong light–matter interaction is usually achieved by embedding a gain medium in a high-quality (Q)-factor cavity made with thick external mirrors. The high reflectivity of the mirrors poses, therefore, a trade-off between pump radiation coupling efficiency and high Q-factor, thus preventing the use of optical cavities in photonic contexts where the photosensitive element necessitates to be readily accessible. Here, this long-standing problem is overcome by engineering “Pseudo-Cavity Modes” (PCM) in a Metal/Dielectric Open Cavity (MDOC) system that has been commonly thought to be incapable to show resonances. The MDOC system lets the embedded fluorophore exposed to radiation, opening to strong light/matter interaction. To prove this: i) exciton/PCM strong coupling regime, with 160 meV Rabi splitting, ii) photoluminescence enhancement by more than 7 times, and iii) polarized and angle-dependent spontaneous emission are experimentally and theoretically demonstrated. The proposed system holds great potential envisioning scenarios like cavity-enhanced photovoltaics, surface-enhanced Raman scattering, open-cavity lasers, photoluminescence steering and polarization.