Gain and lasing in two-level optically dense resonance media without population inversion based on cooperative phenomena upon interaction of light with matter

A new approach to the development of sources of coherent radiation is studi ed both theoretically and experimentally. The approach is based on parametr ic excitation of collective modes of the ''field + atoms" system in two-lev el resonance media without population inversion, with the super-critical co upling between the field and matter subjected to stimulated modulation. The theoretical results include a description of computer simulation of the ga in and stimulated emission based on quantitative formalism of the semiclass ical theory of laser physics (Maxwell-Bloch equations). Experimental study of coherent light amplification in optically dense media without population inversion was carried out using a multimode pulsed dye laser in the two-wa ve pump-probe configuration. As the absorbing medium, we used the positive column of a glow discharge with metastable Ne atoms. A qualitative agreemen t is demonstrated between the data of numerical simulation and experimental spectral characteristics and dynamics of coherent amplification and lasing .