Polarization properties of photon Bose-Einstein condensates (2506.06141v1)

Abstract: The first experimental realization of a photon Bose-Einstein condensate was demonstrated more than a decade ago. However, the polarization of the condensate has not been fully understood and measured in this weakly driven-dissipative system. In this letter, we experimentally investigate the polarization of thermal and condensed light depending on the power and polarization of the pump beam. With full control over the polarization of the pump, it is possible to create arbitrary states on the surface of the Poincar\'e sphere. We show that, in agreement with previous theoretical work, there is a remarkable increase in the polarization strength of the condensate above the threshold for a fully linearly polarized pump. Above a certain threshold also the degenerate orthogonal polarized state of the cavity is occupied, limiting the degree of polarization to approximately 90%.