This paper demonstrates Bose-Einstein condensation (BEC) of photons in a broad-area vertical-cavity surface-emitting laser (VCSEL) with slight cavity-gain spectral detuning. A BEC in the fundamental transversal optical mode was observed at a critical phase-space density. Experimental results followed the equation of state for a two-dimensional Bose gas, despite extracted spectral temperatures being lower than the device's, attributed to the driven-dissipative nature of the photon gas. Higher-order modes showed non-equilibrium lasing in more negatively detuned devices. This work opens avenues for exploring superfluid physics of interacting photons and enables single-mode high-power emission from large-aperture devices.

Maciej Pieczarka, Marcin Gębski, Aleksandra N. Piasecka, James A. Lott, Axel Pelster, Michał Wasiak, Tomasz Czyszanowski