We study the problem of high temperature Bose-Einstein condensation (BEC) of atom-light polaritons in a waveguide cavity appearing due to interaction of two-level atoms with (non-resonant) quantized optical radiation, in the strong coupling regime, in the presence of optical collisions (OCs) with buffer gas particles. Specifically, we propose a special biconical waveguide cavity (BWC), permitting localization and trapping of low branch (LB) polaritons imposed by the variation of the waveguide radius in longitudinal direction. We have shown that critical temperature of BEC occurring in the system can be high enough -- few hundred Kelvins; it is connected with photon-like character of LB polaritons and strongly depends on waveguide cavity parameters. In the case of a linear trapping potential we obtain an Airy-shaped polariton condensate wave function which, when disturbed out of equilibrium, exhibits small amplitude oscillations with the characteristic period in the picosecond domain.
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