Design And Study On Optical Sensing Of Multi-band Perfect Absorption Metamaterials Based On Plasmonic Resonances

In nanophotonics,the interaction between a photon and a substance which triggers an evanescent wave propagating along the metal surface is called surface plasmon polaritons(SPPs).Surface plasmon polaritons can achieve effects such as enhanced Raman scattering,photocatalysis,and optical transmission enhancement.Metamaterials are a new class of materials discovered when exploring nano-optical devices.Metamaterials based on metal surface plasmon resonance have attracted public attention due to their unique physical properties such as perfect absorption and negative refractive index effects.The fields of simplicity,high integration,low cost,ultra-compact sensors,and solar cells have become research hotspots in recent years.However,there are still some problems in the field of high-quality optical sensing,such as narrow incidence angles,polarization sensitivity,single-band and low sensing sensitivity.In this paper,two multi-band perfect absorption metamaterial structures are constructed based on the metal surface plasmon resonance.The finite-difference time-domain method is applied to construct the model and perform numerical simulation,optimization,and related mechanism exploration to achieve high-quality multi-band optical sensing.The layout of the thesis is stated as follows :1.The research background,metamaterials and the research status of perfect absorbers based on plasmonic metamaterials were introduced.2.The theoretical basis of the multi-band metamaterial absorbers was introduced: the development,basic properties,dispersion relations and excitation modes of the surface plasmons,the sensing characteristics of the metamaterial absorbers;and the principle and advantages of the selected numerical calculation method.3.The research designed and researched a dual-band surface plasmonic metamaterial absorber,and realized a dual-band perfect absorption band in the visible-near infrared band whose absorption rate can reach 99.7%.The absorber also has the characteristics of insensitivity to polarization and insensitivity to large-angle incidence,and its sensitivity reaches 783.7 nm/RIU.4.A three-band surface plasmonic metamaterial absorber was designed andstudied.Three near-perfect resonance absorption peaks were obtained in the near-infrared band.The full width at half maximum(FWHM)of the resonance peak was less than 30 nm and the absorption intensity was greater than 99%.In addition,changing the offset of the prismatic hole in the x direction of the structure results in a new near-perfect absorption peak,and a four-band metamaterial perfect absorber was obtained.At the same time,the absorber also has significant advantages such as polarization insensitivity and sensitivity to changes in the surrounding refractive index,and can be used to detect glucose concentration.In summary,the structures designed above have the characteristics of the multiband absorption band,perfect absorption,insensitivity to polarization,insensitivity to large-angle incidence,and high sensitivity to refractive index changes in the surrounding environment,which have a wide range of applications and developments in plasma sensing and bio-molecule detection.