Absorber,Fano Resonance And Application Research Based On Metasurface

The local surface plasmon resonance properties of noble metal composition nanostructures are strongly affected by their nanostructure morphology,size,gap,metal type,and the refractive index of the surrounding medium.Nanostructure of noble metal is a very important research subject in nano science because of peculiar optical properties.Compared with traditional optical devices,nanostructures not only are suitable for integration,but also can break through the optical diffraction limit since the sizes of these nanostructures are very small.Generally,the nanostructures show fancy potential applications in the solar cells,sensors,filters,and so on.In the thesis,we proposed a metasurface that can achieve dual-band coherent perfect absorption?CPA?.Two nearly-perfect CPAs occur at?₁=11.86?m,?₂=13.88?m with absorption intensities of 100%,100%,respectively.The relationship between the length of the metal patch,the refractive index of the dielectric layer and the coherent absorption wavelength are linear,which is useful for enabling CPA at particular wavelengths.The coherent absorption at each operating wavelength can be independently modulated from 1 to nearly 0 by changing the phase difference between the two coherent waves,it revealed the angle-insensitive property of the metasurface and its potential applications.The scalability of magnetic dipole resonance enables our proposed metasurface operating from optical to terahertz range.For example,we developed metasurface that can achieve three bands wide-angle broadband absorption,the average absorptivity is 98%between 19THz and 19.34THz and the bandwidth is 340GHz,the average absorptivity is 97%between 19.93THz and20.29THz and the bandwidth is 360GHz,the average absorptivity is 97.1%between21.205THz and 21.505THz and the bandwidth is 300GHz,respectively.We have proposed infrared four-band absorber based on metasurface,the absorption intensity of resonant peak is 98%,89.2%,98.14%and 99.2%respectively.Moreover,we have proposed a terahertz triple-band metasurface absorber.The result showed that the absorber has three distinctive absorption peaks at 4.86,7.02,and 9.56 THz with absorption rates of 96.3%,98.8%,and 98.4%,respectively.The absorption performance is insensitive to polarized and angle-insensitive.Meanwhile,it could be used for very sensitive refractive sensing.We also have studied the phenomenon of Fano resonance on dual-band and wide band structure,and found that there are strong Fano peak at the corresponding wavelength,which has characteristics of narrow line width and local electric field enhancement.In this paper,a more comprehensive parameter M is proposed to determine performance of Fano resonance.The Fano resonance is closely related to its structural parameters,performance of Fano resonance are optimized through structural parameters.The sensing property analysis is performed under the structure parameters optimized.For Fano resonance of dual-band structure,Changes in the four over ten thousand of the refractive index can be detected through the accurate calculation and analysis.The relationship between resonance wavelength and refractive index of surrounding environment are linear,and the biggest sensitivity of resonance wavelength with refractive index drift is about 5469 nm/RIU.For Fano resonance of wide band structure,Changes in the one over thousand of the refractive index can be detected,and the sensitivity of resonance wavelength with refractive index drift is about 5395 nm/RIU,which can provide effective theoretical references for the refractive index sensing.In order to meet its application in the field of nano photonics,we studied more apparent,fine Fano resonance line shapes,with stronger local electromagnetic field enhancement through the design of structural parameters.