Negative submillimeter absorption in tunnel-coupled quantum wells under resonant infrared excitation

Abstract

We have studied the redistribution of the electrons between the tunnel-coupled ground levels in double quantum wells (DQWs), caused by the resonant infrared (IR) excitation on the next level and relaxation of the photoexcited electrons due to spontaneous emission of the optical phonons. The condition for the inversion of the electron populations in the tunnel-coupled pair of ground states is presented as a function of the DQWs parameters. Negative absorption coefficient of the submillimeter radiation under intensive (2–4 kW/cm2) IR pumping and commonly realized parameters of DQWs is of order 20–50 cm−1.