PD Dr. Axel Pelster
Universität Kaiserslautern

Photon BECs in dye-filled microcavities and VCSELs

The talk provides an overview of current theoretical challenges for describing a photon Bose-Einstein condensate (BEC), which represents a modern prime example for an open dissipative quantum many-body system. In the original experimental platform of dye-filled microcavities the technique of direct laser writing allows to microstructure potentials with different geometries on the mirror surfaces. In this way soon lattices of coupled photon condensates containing hundreds of individual sites are realizable, which are expected to have spiral vortices. We show that their shape can be approximately determined analytically with a projection optimization method, which extends the variational optimization method for BECs of closed systems to open-dissipative condensates. Furthermore, quite recently photon BECs were also observed in vertical cavity surface-emitting lasers (VCSELs). Here frequent photon absorption and emission processes occur due to the creation and annihiliation of electrons and holes in the semiconductor device, yielding a thermalization of photons. This indicates that photon BECs can be a much more common phenomenon in laser physics than previously anticipated.