Raman terahertz Si:P and Si:Sb lasers

Abstract

In the past few years significant progress has been made towards silicon-based lasers mainly due to new approaches in the infrared wavelength range, such as silicon nanocrystals, A-centre mediated direct recombination, Si/SiO2 and Si/SiGe superlattices, porous silicon, erbium-doped silicon, silicon light-emitting diodes, as well as 1.67 µm Raman silicon laser. Recently achieved optically pumped silicon terahertz lasers involve light scattering at donor centre states coupled by resonant interaction with an intervalley transverse acoustic g-TA phonon in silicon. Raman-type Stokes stimulated emission has been obtained from silicon crystals doped by antimony and phosphorus donors at low temperatures when optically excited by radiation from a tunable infrared free electron laser. The photon energy of the terahertz laser emission is equal to the pump photon energy reduced by the energy spacing between a singlet and a doublet donor states in silicon. The lasers emit a few tenths of mWs in a few ps pulse in the frequency ranges of 4.6 - 5.8 THz (Si:Sb) and 6.0 - 6.4 THz (Si:P) and have a gain of ~10^-3 1/cm at a pump intensity of ~100 kW/cm2. Raman-type silicon lasers based on a light scattering on donor centres can be potentially expanded onto mid-infrared lasing, where they could have higher gain and operation temperatures