In this work we propose and analyze the possibility of creating terahertz plasmon-emitting graphene-channel transistor. It is shown that at electric pumping the damping of the terahertz plasmons can give way to their amplification, when the real part of the dynamic conductivity of graphene becomes negative in the terahertz range of frequencies due to the interband population inversion.

Magnetoabsorption in far and mid IR ranges in double HgTe/CdHgTe quantum wells with inverted band structure has been studied in high magnetic fields up to 30 T. Numerous intraband and interband transitions have been revealed in the spectra and interpreted within axial 8 × 8 k·p model. Splitting of dominant magnetoabsorption lines resulting from optical transitions from hole-like zero-mode Landau level has been discovered and discussed in terms of a built-in electric field and collective phenomena.