  We study the characteristics of photogenerated electron-hole plasma in
optically pumped graphene layers at elevated (room) temperatures when the
interband and intraband processes of emission and absorption of optical phonons
play a crucial role. The electron-hole plasma heating and cooling as well as
the effect of nonequilibrium optical phonons are taken into account. % The
dependences of the quasi-Fermi energy and effective temperature of optically
pumped graphene layers on the intensity of pumping radiation are calculated.
The variation of the frequency dependences dynamic conductivity with increasing
pumping intensity as well as the conditions when this conductivity becomes
negative in a certain range of frequencies are considered. %
  The effects under consideration can markedly influence the achievement of the
negative dynamic conductivity in optically pumped graphene layers associated
with the population inversion and, hence, the realization graphene-based
terahertz and infrared lasers operating at room temperatures.
