Research On Tunable THz Surface Plasmon Polaritons And Radiation Source

The THz wave is an electromagnetic wave with a frequency of 0.1 THz-10 THz.Its unique wavelength characteristics make it widely used in biomedical imaging,semiconductor materials and terahertz communications.In THz frequency band,once the processing of the terahertz device based on the metal or medium structure is completed,the performance is also fixed,and the electromagnetic wave can not be controlled.The main purpose of this thesis is to design tunable terahertz surface plasmon polaritons(SPPs)and terahertz radiation sources by using the parametric tunability of plasma or graphene.The paper first introduces the development history and application of surface plasmon polariton,and the research status of terahertz radiation source.Based on this,the relationship between the dispersion of the plasma and the surface of the medium is deduced in detail and the plasmonic properties of the tunable surface are analyzed.Finally,the graphene-based metal-loaded metal grating structure was designed by CST simulation software,and the characteristics of tunable terahertz radiation source were analyzed.The main work of this thesis is as follows:(1)The Maxwell equation was used to derive the dispersion equation between the magnetized plasma and the surface of the medium,and the surface plasmon polariton characteristics were analyzed.The results show that under the non-magnetization condition,the wave vector of SPPs on the plasma surface is larger than the wave vector of photons in the air and the SPPs can not be excited.Therefore,measures of wave vector compensation are needed.However,the dispersion curves of the SPPs and the dispersion curves of the electromagnetic waves in the vacuum plasma produced an intersection point,indicating that the wave-vector matching conditions are satisfied and the SPPs can be excited at this point.The collision frequency of the plasma becomes smaller,the loss caused by the collision is smaller,the SPPs are more easily excited,the applied magnetic field increases,and the matching frequency of the excited surface plasmon becomes lower.(2)The graphene-covered grating structure is designed and its tunable terahertz radiation characteristics are studied.By comparing the intensity of terahertz radiation generated by graphene with that of metal grating without adding graphene respectively,it can be found that graphene can effectively enhance terahertz radiation and change the chemical potential of graphene to obtain a tunable frequency Terahertz radiation source.In addition,the structural parameters of the metal grating changes,dielectric permittivity changes,will affect the excitation of the SPPs frequency,thereby affecting the frequency of generating terahertz radiation.