  We introduce a classical phasor model for the description of multimode photon
condensates that thermalize through repeated absorptions and reemissions by dye
molecules. Thermal equilibrium is expressed through the fluctuation-dissipation
relation that connects the energy damping to spontaneous emission fluctuations.
We apply our model to a photonic Josephson junction (two coupled wells) and to
one- and two-dimensional arrays of photon condensates. In the limit of zero
pumping and cavity losses, we recover the thermal equilibrium result, but in
the weakly driven-dissipative case in the canonical regime, we find suppressed
density and phase fluctuations with respect to the ideal Bose gas.

Optics;Quantum Gases