Two-dimensional UV femtosecond stimulated Raman spectroscopy for molecular polaritons: dark states and beyond

TL;DR

This paper introduces a novel femtosecond UV stimulated Raman spectroscopy technique for real-time observation of molecular polariton dynamics, including dark states, in optical cavities, revealing new insights into their coupling with vibrations.

Contribution

It develops a multidimensional UV-FSRS method and a microscopic theory to detect and analyze dark states and their dynamics in molecular polaritons.

Findings

Dark states signatures identified via UV-FSRS

Real-time monitoring of polariton-vibration coupling

Microscopic theory reveals population and coherence dynamics

Abstract

We have developed a femtosecond ultra-voilet (UV) stimulated Raman spectroscopy (UV-FSRS) for $N$ molecules in optical cavities. The scheme enables a real-time monitoring of collective dynamics of molecular polaritons and their coupling to vibrations, along with a crosstalk between polariton and dark states. Through multidimensional projections of the UV-FSRS signal, we identify clear signature of the dark states, e.g., pathways and timescales that used to be invisible in resonant technique. A microscopic theory is developed for the UV-FSRS, so as to reveal the polaritonic population and coherence dynamics that interplay with each other. The resulting signal makes the dark states visible, thereby providing a new technique for probing dark state dynamics and their correlation with polariton modes.