Negative absorption coefficient of a weak electromagnetic wave caused by electrons confined in rectangular quantum wires in the presence of laser radiation

Analytic expressions for the absorption coefficient (ACF) of a weak electromagnetic wave (EMW) caused by electrons confined in rectangular quantum wires (RQWs) in the presence of laser radiation are calculated using the quantum kinetic equation for electrons in the case of electron-optical phonon scattering. The dependence of the ACF of a weak EMW on the intensity E01 and the frequency Ω1 of the external laser radiation, the intensity E02 and the frequency Ω2 of the weak EMW, the temperature T of the system and the size L (Lx and Ly) of the RQWs is obtained. The results are numerically calculated and discussed for GaAs/GaAsAl RQWs. The numerical results show that the ACF of a weak EMW in RQWs can have negative values. Thus, in the presence of laser radiation, under proper conditions, a weak EMW is increased. This is different from the similar problem in bulk semiconductors and from the case without laser radiation.