TERAHERTZ WAVE AMPLIFICATION, STIMULATED BY DC ELECTRIC-CURRENT, IN GRATING-COUPLED LOW-DIMENSIONAL ELECTRON-SYSTEMS

We present an analytic theory of the transmission of electromagnetic w aves through a structure ''two-dimensional electron system with a flow ing current -grating coupler.'' The transmission coefficient T(omega,n u(dr)) is calculated as a function of frequency, drift velocity nu(dr) ,, and other physical and geometrical parameters of the structure. Thr eshold conditions for amplification [ T(omega nu(dr)) > 1] are analyze d. A number of ideas for a reduction of the threshold velocity and an enhancement of the amplification are proposed. Our results can be used for designing tunable solid-state terahertz wave amplifiers (generato rs), based on the grating coupled low-dimensional electron systems. (C ) 1997 American Institute of Physics.