Mechanism of Stimulated Raman Scattering in Silicon Doped with Helium-Like Donors

Silicon doped with neutral helium-like magnesium donors is studied theoretically as an active medium in the THz frequency range. The inversion mechanism in Si:Mg under optical excitation does not have the necessary efficiency due to the presence of fast relaxation processes. On the contrary, the mechanism of stimulated Raman scattering (SRS) is less sensitive to relaxation times and allows the lasing spectrum to be tuned. An important feature of doubly charged donors is the presence of two Stokes shifts in the system, which significantly expands the range of laser frequencies. Calculations show that the combined use of uniaxial crystal strain and excitation quantum energy tuned in the range of 95‒105 meV (23‒25.5 THz) will make it possible to obtain Raman lasing in the frequency band of 7‒33 meV (~1.5‒8 THz).