Studies On Manipulation Of Electromagnetic Wave Based On Surface Plasmon

Surface plasmon is a surface electromagnetic mode produced by the interaction between light and matter.The electromagnetic field can be localized within subwavelength scale based on surface plasmon resonant structures.As a result,surface plasmon structures have been widely studied and applied in information transmission,optical sensing,photo detection and display.In this thesis,we applied the surface plasmon resonance structure into waveguide structure,metal dielectric grating structure,electromagnetically induced transparency structure and polarization conversion structure to manipulate electromagnetic wave.We first studied the manipulation of electromagnetic wave based on waveguide structure.A surface plasmon resonance structure based on metal dielectric metal waveguide coupled with resonator was designed.Based on this structure,high performance band stop filtering and optical sensing in near infrared region were realized.By the coupling between the waveguide and a resonant cavity,we studied the band stop filtering properties of a rectangular cavity and a circular cavity.The transmission characteristics of the rectangular cavity and circular cavity were analyzed theoretically and the improvements of performance for the double-cavity structure compared with a single cavity were studied.The influence of structural parameters on the transmission spectra and sensing performance were investigated in detail.A sensitivity of 1136 nm/RIU with a high figure of merit of 51275 could be achieved at the resonant wavelength of 1148.5 nm.The resonant wavelength of the structure could be tuned by changing the geometric parameters.In terms of electromagnetic absorber,we designed a perfect absorber composed of metal dielectric metal structure based on the basic principle of metamaterial perfect absorber.The absorption mechanism of the absorber was analyzed in detail,and the field distribution of absorber at absorption peak was studied.By changing the structural parameters of absorber,the influence of the width of metal wire,the height of metal wire,the thickness of dielectric layer and the period on the absorption characteristics of absorber were investigated.The results showed that the absorber presented different absorption characteristics under different metal wire width conditions.The absorption mechanism of the structure with small duty cycle was mainly the coupling effect between metal wire and metal film,while the absorption mechanism with large duty cycle was mainly the FP resonance effect of air cavity.In order to achieve ultra-narrow band perfect absorption,we designed a perfect absorber based on double metal dielectric structure.The absorber achieved perfect absorption with a bandwidth of 0.85 nm in the near infrared region.We discussed the absorption mechanism of the narrow band absorber and compared it with the metal grating structure.Finally,we studied the influence of structural parameters on its absorption performance and studied its sensing performance.In the past,metal is the main material of surface plasmon resonance structure.However,in order to dynamically control the resonance structure based on metal material,we have to change the geometric parameters of the structure or introduce other active control materials,which limits its application.Graphene is an ideal material for active control of surface plasmon due to its dynamic tuning properties in terahertz to infrared region.In order to achieve dynamic control of electromagnetic wave,we designed surface plasmon resonant structures based on graphene metamaterials.We designed a plasmon induced transparency structure based on graphene metamaterial which was composed of graphene strip structure and split ring structure.We analyzed the optical properties of strip structure and split ring structure and investigated the influence of structural parameters on the structures.The resonant frequency of the strip structure decreased with the increase of its length while it increased with the increase of its width.For the split ring structure,the resonant frequency decreased with the increase of arm length and arm spacing,and increased with the increase of its width.Then we designed the plasmon induced transparency structure with a transparent window at 4.23 THz.The principle of the structure was the interference between the bright mode generated by the strip and the dark mode generated by the split ring.The transmission properties of the structure were fitted by the coupled mode theory and it showed that the near field coupling led to the transfer of energy from strip to split ring structure.At last,we investigated the tuning properties of the structure.By changing the Fermi level of graphene,we could effectively change the transparent window of the structure and produce a picosecond group delay at the transparent window.Polarization converter based on electromagnetic metamaterials have been widely investigated.However,there are still some problems.First,the polarization conversion efficiency and the conversion bandwidth still need to be improved.Expansion of bandwidth is often based on the combination of multi-layer structures or multiple sub cell structures.Secondly,polarization converter based on metal material is not easy to be tuned.In order to deal with these problems,we proposed a polarization conversion structure based on graphene metamaterial which could improve the conversion efficiency and achieve dynamic tuning properties.We designed a reflective linear polarization converter and analyzed the conversion mechanism of the structure.The polarization converter was based on cross rectangular structure and it presented a broad conversion band with a high polarization conversion ratio bigger than 95% in terahertz frequency over a broad bandwidth from 6.68 THz to 8.66 THz which was 25.8% of the central frequency.The basic mechanism of wideband polarization conversion was the mode mixing between two rectangular structures.The results showed that changing the length of the rectangle could turn the broadband conversion into dual band conversion and changing the thickness of the dielectric layer could change the conversion efficiency.By changing the Fermi level of graphene,the converter could be dynamically tuned from 4.5 THz to 10.5 THz.The converter showed high conversion efficiency for a wide range of incident angles from 0 to 40?.By changing the period,the converter could work in different frequency band with high conversion efficiency and broad bandwidth.By applying the basic principle of surface plasmon resonance,we have designed manipulation of electromagnetic wave based on metal and graphene materials.We have realized the manipulation of the amplitude,polarization and delay of electromagnetic waves.These structures have potential applications in optical sensing,imaging and communications and provide references for further research.