Propagation Characteristics of Broadband Terahertz Waves in an Inhomogeneous Plasma With Sheath

Using terahertz (THz) waves as the communication carrier is an effective way to overcome the blackout when a spacecraft reenters the atmosphere. A blackout plasma typically has a sheath, but the physical mechanism of broadband THz wave propagation and attenuation in sheath plasma has not been clarified. This article presented experimental and theoretical studies of the propagation characteristics of broadband THz waves in a neon plasma with a sheath for plasma densities ranging from 1017 m-3 to 1018 m-3. The experimental results showed that a broadband THz wave at a frequency of 1.9 THz had a high attenuation of about 22 dB in the plasma. We simulated the propagation characteristics of the THz wave in the plasma, based on a five-layer plasma model by using the scattering-matrix method. When the sheath plasma density, simulation parameter, was 1021 m-3, the experimental attenuation curve of THz wave in plasma was consistent with the simulation curve. This work clarified the determinants of THz wave attenuation in sheath plasma, which lays a foundation for overcoming the black barrier problem.