# Controlled and robust two-mode emission from the interplay of driving and thermalization in a dye-filled photonic cavity

## TL;DR

This paper investigates how the interplay of thermalization and driven-dissipative processes in dye-filled photonic cavities enables controlled two-mode emission, with potential applications in photonic device engineering.

## Contribution

It reveals a robust mechanism for two-mode emission driven by off-centered pumping and thermalization, and demonstrates how to tune emission thresholds via potential landscape design.

## Key findings

- Two-mode emission arises from interplay of thermalization and pumping.
- Threshold pump power can be tuned by modifying the potential landscape.
- System exhibits a transition from lasing in excited mode to ground mode.

## Abstract

Two dimensional photon gases trapped in dye-filled microcavities can undergo thermalization and nearly ideal equilibrium Bose-Einstein condensation. However, they are inherently driven-dissipative systems that can exhibit an intricate interplay between the thermalizing influence of the environment given by the dye solution and the pump and loss processes driving the system out of equilibrium. We show that this interplay gives rise to a robust mechanism for two-mode emission, when the system is driven by an off-centered pump beam. Namely, after the system starts lasing in the dominantly pumped excited mode, in a second transition a photon condensate is formed in the ground mode, when the pump power is increased further. This effect is a consequence of the redistribution of excited dye molecules via the lasing mode in combination with thermalization. We propose to exploit this effect for engineering controlled two-mode emission and demonstrate that by tailoring the transverse potential landscape for the photons, the threshold pump power can be tuned by orders of magnitude.