Coherent Terahertz Radiation Generation Assisted by Low-Temperature Optical Phonon Emission: Achievements and Perspectives

The conditions for THz radiation generation caused by electron transite time resonance in momentum and real spaces under low-temperature optical-phonon emission are analyzed. It is shown that such a phenomenon provides a unique possibility to realize the sub-THz and THz radiation generation at the border of the electrooptical and electronic techniques by using both the approaches: (i) amplification of transverse electromagnetic waves in 3D bulk materials and 2D quantum wells, and (ii) longitudinal current instabilities in submicron and overmicron n⁺nn⁺ diodes.