Strange lifetimes of the vibrations of interstitial oxygen in SiGe alloys

New principles to generate stimulated emission in terahertz frequency range from silicon doped by shallow donor centers have been demonstrated. Lasing in the frequency bands covering the range of 4.5–6.4 THz has been achieved from silicon crystals doped by all group-V donors under optical pumping by radiation of frequency-tunable mid-infrared free electron laser at cryogenic temperatures. Analysis of the data shows that the emission corresponds to Stokes-shifted Raman-type lasing. The Stokes shift is determined by the 1s(E)–1s(A1) donor electronic resonance.