Stimulated terahertz emission from arsenic donors in silicon

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Abstract
Stimulated emission has been obtained from intra-center donor transitions in silicon monocrystals doped by arsenic. The Si:As laser was optically excited by radiation from a CO2 laser. The emission spectrum consists of two lines corresponding to the 2p±-->1s(E) and 2p±-->1s(T2) intra-center arcenic transitions. The population inversion is formed due to fast 2s-->1s(A1) electron relaxation assisted by intervalley longitudinal acoustic f-phonon emission. This keeps the excited donor states below the 2p± state unpopulated. Thus population inversion occurs between the 2p± state and the 1s(E), 1s(T2) states