Effect of molecular absorption and vibrational modes in polariton assisted photoemission from a layered molecular material

TL;DR

This study investigates how molecular absorption, vibrational modes, and the number of layers influence polariton-assisted photoemission in a layered molecular material coupled to a microcavity, revealing differences in strong coupling signatures and the role of Raman scattering.

Contribution

It provides new insights into the effects of vibrational modes and layer number on polariton-assisted emission, highlighting differences between reflection and photoluminescence signatures.

Findings

Raman scattered photons significantly populate the lower polariton branch.

Polariton-assisted photoemission depends on molecular absorption modification.

Differences observed between reflection spectroscopy and photoluminescence signatures.

Abstract

The way molecules absorb, transfer, and emit light can be modified by coupling them to optical cavities. The extent of the modification is often defined by the cavity-molecule coupling strength, which depends on the number of coupled molecules. We experimentally and numerically study the evolution of photoemission from a thin layered J-aggregated molecular material strongly coupled to a Fabry-Perot microcavity as a function of the number of coupled layers. We unveil an important difference between the strong coupling signatures obtained from reflection spectroscopy and from polariton assisted photoluminescence. We also study the effect of the vibrational modes supported by the molecular material on the polariton assisted emission both for a focused laser beam and for normally incident excitation, for two different excitation wavelengths: a laser in resonance with the lower polariton branch, and a laser not in resonance. We found that the Raman scattered photons play an important role in populating the lower polariton branch, especially when the system was excited with a laser in resonance with the lower polariton branch. We also found that the polariton assisted photoemission depends on the extent of modification of the molecular absorption induced by the molecule-cavity coupling.