Thermodynamics of nonequilibrium radiation. (II) Irreversible evolution and experimental setup

Giving continuation to the study of the thermodynamics of nonequilibrium radiation presented in the preceding article [Physica A 300 (2001) 386], we derive the evolution in time of its macroscopic nonequilibrium state. The case of a semiconductor sample and the coupling of radiation and transverse optical phonons is explicitly considered. Excitation of the latter drives the radiation field out of equilibrium. Under constant excitation, a steady state sets in which is analyzed. It is shown that the quasitemperature per mode of the radiation field, which has been defined in the preceding paper, can be determined in optical experiments such as Raman scattering.