Terahertz lasers based on shallow impurities in silicon and germanium

Abstract

Different principles to generate stimulated emission from semiconductors in the terahertz frequency range are being under intense research nowadays due to prospective compact low-consuming devices for diverse applications in solid-state spectroscopy, radio astronomy, security control, communication techniques. Silicon-based semiconductors offer low optical loss and high thermal conductivity for broad-band terahertz laser media. These can be used, for instance in the range between 5 and 7 THz where GaAs-based quantum cascade lasers suffer from significant lattice absorption. Recently optically pumped germanium and silicon lasers operating on transitions between particular impurity levels as well as intracenter Raman silicon laser have been realized and thoroughly investigated towards their operational limits. Different laser schemes realized for the 1-7 THz terahertz frequency range will be discussed with emphasis on physical principals of the lasers. These approaches have demonstrated for the first time the potential of principle phonons for intersubband and intracenter laser mechanisms. The realization of intracenter lasers demonstrates the possibility of using different principle phonons in semiconductors for generation of stimulated emission in the mid- and far-infrared wavelength range.