Femtosecond dynamics of a polariton bosonic cascade at room temperature

TL;DR

This paper visualizes femtosecond polariton dynamics in a room-temperature bosonic cascade within a ZnO whispering gallery microcavity, revealing ultrafast condensation and scattering processes crucial for optical technologies.

Contribution

It provides the first direct visualization of femtosecond polariton cascade dynamics at room temperature using spectroscopic imaging.

Findings

Observation of ladder-form build-up of polariton condensates

Distinction of polariton parametric scattering on femtosecond timescales

Modeling of dynamics with rate equations matches experimental data

Abstract

Whispering gallery modes in a microwire are characterized by a nearly equidistant energy spectrum. In the strong exciton-photon coupling regime, this system represents a bosonic cascade: a ladder of discrete energy levels that sustains stimulated transitions between neighboring steps. In this work, by using femtosecond angle-resolved spectroscopic imaging technique, the ultrafast dynamics of polaritons in a bosonic cascade based on a one-dimensional ZnO whispering gallery microcavity is explicitly visualized. Clear ladder-form build-up process from higher to lower energy branches of the polariton condensates are observed, which are well reproduced by modeling using rate equations. Moreover, the polariton parametric scattering dynamics are distinguished on a timescale of hundreds of femtoseconds. Our understanding of the femtosecond condensation and scattering dynamics paves the way towards ultrafast coherent control of polaritons at room temperature, which will make it promising for high-speed all-optical integrated applications.