Polarization characteristics of the stimulated emission of PbSe crystals during two-photon pumping that derive from the selective population of energy valleys

The polarization characteristics of the stimulated recombination emission from PbSe crystals at liquid-helium temperatures are investigated. It is found that, as a result of the selective population of energy valleys brought about by the linearly polarized radiation of a CO2 laser, unique polarization dependences of the recombination emission are observed. These are explained by the preferred contribution of individual valleys and by the gain of the polarization modes. The high degree of polarization in the stimulated recombination emission from PbSe (up to 0.54) observed in the experiment significantly exceeds the level that is theoretically possible for spontaneous linear recombination (0.065); this is seen as attesting the large gain in the PbSe crystal under stimulated emission.