Population Dynamics for System of Exciton, Bi-Exciton and Photon

The study of time development is indispensable for a system of excitons and bi-excitons at high density because this exists only as a transient state. Here we study theoretically the population dynamics of excitons and bi·excitons both under the. pulse and steady excitations where photons and phonons emitted in the chemical processes of this system can be considered as the irrelevant external system. Under the opposite condition where the radiation field composes the relevant system, the laser action due to the radiative decay of bi ·excitons is discussed.