Study On The Attenuation Characteristics Of THz Wave In Atmosphere

THz wave located at a special region in the electromagnetic spectrum, THz wave located between electrical field and optic field, which make the THz wave has many unique advantages, such as, low photon energy, transient, broadband and transmission.These characteristics determine that in biomedical, imaging, safety monitoring and space communication and sensing field THz wave has a broad application prospect. If we want to apply THz wave in the field of space communication, atmospheric remote sensing and radar detection, the study of attenuation characteristic of THz wave in atmospheric environment will play an important role.The main content of this article is as follows:1. In this article, We analyzed the enhancement and attenuation of THz radiation transmitted in atmosphere with radiation transfer equation. When THz wave transmit in the atmosphere, the gas molecules and aerosol particles interact in the atmosphere will cause the enhancement or attenuation, enhancement caused by thermal radiation and the attenuation caused by absorption and scattering.2. In this article we calculated the atmosphere transmission characteristics of THz wave in a sunny or cloudy weather. The spectral line parameters of Oxygen,water vapor and other atmospheric molecules were extracted from the HITRAN database, with these parameters we calculate the low-frequency terahertz wave attenuation in the atmosphere.3. In this article we calculated the scattering efficiency factor of single scattering,the scattering cross section, the scattering phase function and the attenuation in the dust that having a certain size distribution with the help of Mie scattering theory. We also use the Monte Carlo method to write programs, with those programs the attenuation characteristic of THz wave in two typical desert in our country are simulated by the programs. The Mie scattering theory correspond to the single scattering occur in low concentration dust, while the Monte Carlo method correspond to the multiple occur the high concentration dust.4. The experiment of measuring the attenuation characteristics of THz was introduced in this article. The experimental apparatus was a test system composed of Fourier transform infrared spectrograph. We also analysis the deficiency of this experiment and put forward an improvement plan.