A source of terahertz coherent phonons

Abstract

Resonant tunnelling in a double-barrier heterostructure (DBHS) designed in order to produce an intense coherent emission of phonons is studied theoretically. Thisemission is achieved when the energy difference between the first excited level and the ground state in the well is close to the LO-phonon energy. The LO phonons emitted during the electron transition decay into a pair of (fLO and TA) phonons that leave the well in the [111] direction. These secondary TA phonons are coherent and form a beam that we call a SASER (by analogy with ‘laser’). The circulating current and the populations of phonons and electrons in the well are calculated by solving appropriate kinetic equations. Some possible applications of this system are discussed.