Silicon Donor and Stokes terahertz lasers

Abstract

In the past few years significant progress has been made towards silicon-based lasers. Numerous approaches in the infrared wavelength range were elaborated to overcome the indirect bandgap structure of silicon, such as nanocrystals, A-centre mediated direct recombination, Si/SiO2 and Si/SiGe superlattices, porous silicon, erbium-doped silicon, and silicon light-emitting diodes. Mid-infrared 1.67 µm Raman silicon laser has been achieved. Recently developed optically pumped silicon-based THz lasers involve direct optical transitions between donor excited states (Intracentre Si Donor laser) or the light scattering at donor centre states coupled by resonant interaction with an inter intervalley transverse acoustic g-phonon in silicon (Brillouin-type Si Stokes laser). Different features of the population inversion mechanisms in the silicon lasers allow covering the frequency range from 1 to 7 THz with a few tenths of mW output power under pumping by mid-infrared pulsed lasers. The laser mechanisms continue a development of basic silicon lasers following the terahertz Si intracentre laser and the infrared Raman Si laser.