Design and application of terahertz near field imaging quasi-optical path

In order to solve the problem of mismatch between the size of the near-field probe and the wavelength of the terahertz beam in the terahertz near field imaging system, the quasi optical transmission path of the near field imaging is designed in this paper. The quasi optical path adopts two off axis parabolic mirrors for the collimation transmission and focusing of terahertz waves respectively. The electromagnetic simulation of the designed terahertz collimating transmission optical path is carried out, and the simulation results show that the collimating transmission and focusing of terahertz waves can be realized effectively. At the same time, the radiation performance of the near field probe in the electrically large and complex environment is simulated. The simulation results show that the quasi optical path can effectively collect the terahertz waves scattered by the probe. Based on the designed terahertz quasi optical transmission path, a terahertz near field imaging system is built and tested. The experimental results show that the quasi optical path can be effectively applied for terahertz near field imaging.