MIRRORLESS LASING ACTION VIA NONLINEAR-INTERACTION BETWEEN PHOTONS AND BOSONS

We study the lasing action due to nonlinear interactions of photons wi th boson elementary excitation, such as phonons and excitons, and poin t out the distinct features from the conventional laser model describe d by the two-level model. External feedback by means of cavity mirrors is unnecessary fdr the lasing action as well as for the increasing ab sorption optical bistability. It is shown that the Landau theory of th e second-order phase transition is applicable to the threshold behavio ur of the present mirrorless laser model.