  We study experimentally the lasing regime of a GaAs based microcavity sample
under strong optical pumping. The very same sample exhibits the strong coupling
regime at low excitation power with a Rabi splitting as large as 15 meV. We
show that some features which may be considered as experimental evidence of
polariton Bose Einstein condensation are also observed in the weak coupling
regime when the cavity is behaving as a regular photon laser. In particular,
the emission pattern in the lasing regime displays a sharp peak near the energy
minimum followed by a Boltzmann distribution at higher energies.
