Advanced THz laser performance of shallow donors in axially stressed silicon crystal

Abstract

Terahertz stimulated emission (4â��6 THz) from optically excited group-V donors (phosphor P, antimony Sb, arsenic As, bismuth Bi) in silicon crystal under compressive force has been studied. Measurements evidence that compressive force of 1â��1.5 kbar for P, Sb and of 2â��3 kbar for As, Bi applied along {100} crystallographic orientations results in the enhancement of the laser gain and enlarges the emission efficiency. At that laser threshold intensity can be decreased by two orders of magnitude. For As and Bi donors it is accompanied by the laser line switching while the 2p0 state turns out to be the upper laser state instead of the 2p�± one. The effect of the uniaxial stress on donor lasing originates from conduction band valley shift which split donor states changing their eigen-values and eigen-functions. According to the calculations of phonon-assisted relaxation rates appropriate donor modification increases the lifetime and makes pump efficiency of the upper laser states better.