UV/vis-to-IR Photonic Down Conversion Mediated by Excited State Vibrational Polaritons

TL;DR

This paper introduces a novel photophysical process where UV/vis excitation creates excited state vibrational polaritons that enable IR emission, opening new avenues in polariton chemistry and quantum transduction.

Contribution

It demonstrates the formation of excited state vibrational polaritons via UV/vis excitation and models their dynamics, proposing a new mechanism for photonic down conversion.

Findings

Identification of PAA as a candidate molecule for ESVP formation

Modeling of ESVP dynamics using the truncated Wigner approximation

Potential applications in sensing and quantum transduction

Abstract

This work proposes a new photophysical phenomenon whereby UV/vis excitation of a molecule involving a Franck-Condon (FC) active vibration yields infrared (IR) emission by strong coupling to an optical cavity. The resulting UV/vis-to-IR photonic down conversion process is mediated by vibrational polaritons in the electronic excited state potential. It is shown that the formation of such excited state vibrational polaritons (ESVP) via UV/vis excitation only occurs with molecules having vibrational modes with both a non-zero FC activity and IR activity in the excited state. Density functional theory calculations are shown to effectively identify a candidate molecule, 1-Pyreneacetic acid (PAA), with this property and the dynamics of ESVP are modeled using the truncated Wigner approximation. Overall, this work presents a new avenue of polariton chemistry where excited state dynamics, driven by photoexcitation, are influenced by the formation of vibrational polaritons. Along with this, the photonic down conversion is potentially useful in both the sensing of excited state vibrations and in quantum transduction schemes.