Controllable far-infrared electromagnetic radiation from plasmas applied by dc or ac bias electric fields

摘要

It is shown theoretically and numerically that a dc/ac bias field applied over tenuous plasma can be converted efficiently into electromagnetic (EM) waves at the plasma frequency ω_p, with the amplitude and polarization determined by the bias. The initial phase of the EM waves can be controlled by the triggering time of the bias and therefore circularly/elliptically polarized EM waves can be obtained by applying two bias fields perpendicular to each other. When the bias frequency is near ω_p, the resonance appears and the EM waves are generated with the intensity enhanced considerably as compared with the dc-bias case. This approach provides a potential way to produce tunable far-infrared EM waves such as terahertz waves. Limits of this approach by available parameters of plasmas and bias are also discussed.