Submillimetre Radiation at Continuous Photoexcitation of CdS Crystals

The laser generation of submillimetre radiation in CdS crystals, excited by pulce radiation of a N2-laser at room and nitrogen temperatures, was reported at a first time in our papers [1,2]. This radiation was explained by us as a result of transitions between exciton subbands, inverse population of them arises due to radiative Auger-recombination of excitons in their ground state. For many applications, in particular in spectroscopy, it is needed to have cw laser radiation tuning in the far infrared. Some indirect provements of the achievment of inverse population of exciton subbands in perfect monocrystals Cds and CdSe, excited by a mercury lamp at helium temperatures have been contained in our paper [3]. The aim of the work was to observe a submillimetre radiation in these conditions. As a result, we have obtained not only expected emmission by excitons, but also the submm radiation due to transitions between states of shallow impurities.