Fig. 2
From: Bose–Einstein condensation of photons in an erbium–ytterbium co-doped fiber cavity
Experimental and theoretical spectra below and above condensation. They are given for different overall powers (photon density) P and temperatures T. The slopes of the almost straight lines in the spectra (λ dependence of hν/kBT) fit the theoretical thermal Bose–Einstein (BE) distribution slope for each temperature shown by the dashed lines. a Experimental spectra at a room temperature (296 K) for various intra-cavity power P values. b Theoretical BE distribution at a room temperature. c Experimental spectra at 153 K. d Experimental spectra at 326 K. The different power P values for the spectra in a, c, d are obtained by increasing the pumping from 0 to 80 μW. e, f show the spectra for various temperatures, each with a fixed power, below and above condensation (P = 1.4 and 80 μW, respectively). We emphasize that the slopes match the various temperatures following the corresponding BE spectra
