Generation Of Terahertz Light Sheet And Its Application In Imaging Systems

Recently,terahertz(THz)wave has aroused general interests at home and abroad due to its unique properties,and has been widely used in non-destructive testing,security inspection,medical and wireless communications.THz structured beam is a type of THz beam with special phase wavefront.Currently,THz Bessel beams,Airy beams and vortex beams has become one of the research highlights.After passing through a ridge prism,THz Gaussian beam will change into a new diffraction-free structured beam,and its shape propagating in free space is similar to a thin sheet,so we call it THz light sheet.In this dissertation,we will focus on the generation,optimization and application of this new THz structured beam.Firstly,the fabrication method of terahertz refractive optical devices used in this dissertation is described.The traditional processing methods of terahertz optical devices are complex and time-consuming.While 3D printing is an additive manufacturing technique in which the materials are stacked layer by layer to form a three-dimensional entity,and no subsequent processing is required.3D printing can be used to efficiently fabricate THz optical devices.Taking cylindrical lens as an example,the basic process of designing and fabricating terahertz optics devices based on 3D printing is demonstrated.The experimental results show that 3D printing THz cylindrical lens has similar focusing performance to the commercial one.Then we study on the generation and optimization of THz light sheet.Based on FDTD numerical simulation,the propagation properties of the THz light sheet are defined,and the influence of the bottom angle of the ridge prism on the maximum non-diffraction distance of the output THz light sheet is studied.THz light sheet is generated experimentally at 0.3 THz,and the experiment results are in good agreement with the simulation.In order to make it more practical,a lens group is designed to optimize the properties of THz light sheet.The experiment results show that the maximum non-diffraction distance of THz light sheet is more than doubled.Finally,the applications of THz light sheet in imaging is explored.Imaging experiments were performed using THz light sheet at 0.3 THz,and the results showed that legible images are obtained within a range of 175 mm of sample placement.