Stress-controlled phonon-impurity resonant interactions in terahertz silicon lasers

Abstract

Silicon terahertz lasers operate at frequencies between 1 THz and 7 THz under conditions of optical mid-infrared or far-infrared pumping and low lattice temperatures (‹30 K). The intracenter laser mechanism is based on optical transitions between excited states of group-V donors P, Sb, As and Bi, while Stokes stimulated light scattering is responsible for lasing in Si:Sb. In both cases population inversion is realized due to different rates of the phonon-assisted intracenter relaxation of captured electrons. The donor states, resonantly coupled by the interaction with intervalley phonons in the Si lattice, exhibit the shortest lifetimes that determines the specific laser schemes in n-Si. External stress applied to a Si crystal can release the resonant phonon-impurity coupling. By this it changes the laser operation transition and its efficiency.