Thermalization Rate of Light in Weakly Coupled Molecular Systems

TL;DR

This paper derives a theoretical expression for the thermalization rate of light in molecular systems with low-frequency vibrations, highlighting how microscopic vibrational properties influence light thermalization in cavities.

Contribution

It introduces a perturbation theory approach for Lindblad superoperators to quantify vibrational contributions to light thermalization in weakly coupled molecular systems.

Findings

Derived a general formula for thermalization rate depending on microscopic vibrational properties.

Provided estimations using macroscopic parameters like light-matter coupling and cavity resonances.

Showed applicability across various cavity designs without specific structural constraints.

Abstract

Emission and absorption spectra of molecular films are impacted by low-frequency molecular vibrations. These vibrations define the linewidths of the absorption and emission spectral peaks, as well as the Stokes shift. In cavities that use a molecular film as an active medium, low-frequency molecular vibrations facilitate the thermalization of light, enabling the formation of Bose-Einstein condensation. In this work, I employ perturbation theory for Lindblad superoperators and derive the contribution of the low-frequency molecular vibrations to the thermalization rate of light in a weak coupling regime between light and matter. The derived thermalization rate applies for any cavity design but depends on the local microscopic properties of low-frequency molecular vibrations. I provide an estimation for the thermalization rate, which requires only knowledge of the macroscopic parameters of the system: light-matter interaction strength, resonant frequencies of the cavity and excitons, number of molecules in the illuminated area, and the linewidth temperature dependence of the 0-0 peak in the emission spectra of standalone molecular film.