Polarization selection rules in exciton-based terahertz lasers

This version is made available in accordance with publisher policies. Please cite only the published version using the reference above. Optical pumping of excited exciton states in semiconductor quantum wells is a tool for the realization of ultracompact terahertz (THz) lasers based on stimulated optical transition between excited (2p) and ground (1s) exciton states. We show that the probability of two-photon absorption by a 2p exciton is strongly dependent on the polarization of both photons. Variation of the threshold power for THz lasing by a factor of 5 is predicted by switching from linear to circular pumping. We calculate the polarization dependence of the THz emission and identify photon polarization configurations for achieving maximum THz photon generation quantum efficiency.