Photon condensation in a cavity pumped semiconductor

Aurelian Loirette--Pelous

The phenomenon of condensation of photons corresponds to the macroscopic population of a cavity mode by photons. Its paradigmatic example is the so-called laser, with the corresponding semiconductor-based devices called laser diode. While lasing is intrinsically an out-of-equilibrium phenomenon, recent experiments \cite{klaers2010,barland2021} demonstrated the possibility to reach equilibrium condensation of photons, the so-called Bose-Einstein condensation regime. Here, we highlight with a simple model the differences between these two regimes in a semiconductor-based device, and then present a numerical method based on a Kirchhoff law generalized to materials in local thermodynamic equilibrium. The latter allows simulating accurately the emitted power taking into account the details of the photonic cavity.