Transmission characteristics of terahertz wave in high temperature plasma

Abstract

In the hypersonic flight, the air surrounding an aircraft under the effect of high temperature will be ionized. The ionized gas is called plasma. Because of the influence of interaction between electromagnetic wave, in some cases the communication will be interrupted. High temperature effect is an important characteristic of the plasma. Therefore, the study of terahertz wave propagation in high temperature plasma is of great significance. In this paper, the transmission of terahertz wave in a high temperature plasma slab is studied. Generally, high temperature plasma is an anisotropic medium. The electromagnetic wave propagates in anisotropic high-temperature plasma and forms left-hand circular polarization mode or right-hand circular polarization (RCP) mode. It is found that the RCP wave can exhibit some novel characteristics, such as the forbidden band transmission characteristics, which is discovered in this paper. The transmission characteristics of terahertz wave in high temperature plasma are studied analytically. The results show that when the frequency of terahertz wave is lower than plasma frequency, the wave cannot be propagated in high temperature plasma, and it shows a stopband characteristic. When the frequency is higher, it can be transmitted through the plasma, and it presents a passband characteristic. These are consistent with the propagation characteristics of electromagnetic waves in cold plasma. However, some characteristics in high temperature plasma are different from those in the cold plasma. In high temperature plasma, the transmission characteristics are influenced by the electron temperature and external magnetic field. When the two parameters are chosen appropriately, a sharp transmission peak will be produced in the stopband. This phenomenon has never been found in cold plasma models before. And the paper will discuss this problem by the two influencing factors. It is also found that the frequency of the transmission peak is affected by magnetic field, and the peak amplitude is influenced by electron temperature. The electron temperatures at high transmittance (transmittance is about 1) under different applied magnetic fields are calculated. In order to study the law embodied in the data, the method of data fitting is adopted. And the formula of transmission peak frequency is obtained by curve fitting. The fitting results show that the transmission peak frequency is proportional to the external magnetic field. The relationship between peak electron temperature and external magnetic field is exponential. Finally, the fitting formula is verified by the finite-difference time-domain method. The numerical results are in good agreement with the analytical solution results, which proves the correctness of the work.