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- ItemTerahertz stimulated emission from silicon doped by hydrogenlike acceptors(College Park : American Institute of Physics Inc., 2014) Pavlov, S.G.; Deßmann, N.; Shastin, V.N.; Zhukavin, R.K.; Redlich, B.; van der Meer, A.F.G.; Mittendorff, M.; Winnerl, S.; Abrosimov, N.V.; Riemann, H.; Hübers, H.-W.Stimulated emission in the terahertz frequency range has been realized from boron acceptor centers in silicon. Population inversion is achieved at resonant optical excitation on the 1Λ8+ → 1Λ7- , 1Λ6-, 1Λ8- intracenter transitions with a midinfrared free-electron laser. Lasing occurs on two intracenter transitions around 1.75 THz. The upper laser levels are the 1Λ7- , 1Λ6- , and 1Λ8- states, and the lower laser level for both emission lines is the 2Λ8+ state. In contrast to n-type intracenter silicon lasers, boron-doped silicon lasers do not involve the excited states with the longest lifetimes. Instead, the absorption cross section for the pump radiation is the dominating factor. The four-level lasing scheme implies that the deepest even-parity boron state is the 2Λ8+ state and not the 1Λ7+ split-off ground state, as indicated by other experiments. This is confirmed by infrared absorption spectroscopy of Si:B.