Research On Ultra-narrow Band Perfect Absorber Based On Surface Lattice Resonance

Nowadays the research on materials has developed from natural materials to artificial metamaterials.Metamaterials with periodic subwavelength nanostructures show unique physical properties.In the field of metamaterials,metamaterial perfect absorbers(MPAs)have attracted extensive attention of scientists.The MPA can achieve nearly 100%perfect absorption of the incident light.Most MPAs are built as sandwich structures with a metal nanoantenna-dielectric layer-metal film(MIM)configuration.Through the excitation of the surface plasmon resonances of the nanoantennas,local electromagnetic field near the surface of metal nanostructure can realize the perfect absorption at the resonance wavelength.However,due to the inevitable Ohmic loss in the metal,the plasmon resonances exhibit low quality factors,which can affect the performance of the device.Some dielectric materials with high refractive index and the small imaginary part of the dielectric constant have low intrinsic loss and rich optical properties,which provide a new platform for the manipulation of light field at the subwavelength scale.In this thesis,we propose an ultra-narrow band perfect absorber based on Mie resonance in high refractive index dielectric materials,and the simulation design is carried out by using FDTD commercial software.In the first part,we use the surface lattice resonance generated by the coupling of the magnetic dipole supported inside the WS₂nanodisk metamaterial and Rayleigh anomaly in the periodic array to achieve the ultra-narrow band perfect absorption in the near infrared with a full-width at half maximum(FWHM)of 15nm,and the absorption reached 99.99%.We studied the influence of the structure parameters on the absorption performance systematically,and the absorption wavelength can be tuned flexibly in the near infrared.Through the analysis of energy loss,it is concluded that the absorption basically occurs inside the metal substrate.Moreover,the surface lattice resonance depend strongly on the environmental refractive index,so the proposed perfect absorber can be used in refractive index sensing and a sensitivity up to 1067nm/RIU is demonstrated.In the second part,the SLR excited in the Si nanocuboid metamaterial array is used to achieve the ultra-narrowband perfect absorption with absorption up to 99%with a full-width at half-maximum(FWHM)of 40nm in the mid-infrared wavelength range.We systematically studied the influence of the structure parameters on the absorption performance,then studied the influence of the polarization incident light in X and Y direction on the absorption performance.It was found that for the perfect absorber with the same size,perfect absorption of the incident light in two polarization directions could be achieved.In addition,we studied the coupling between the MPA and thin hexagonal boron nitride(h BN)layers laid on top of the Si metamaterial.Splitting of the absorption spectrum is observed due to the coupling between the h BN phonon and the surface lattice resonance of the Si MPA.These two high refractive index metamaterials provide a new approach to achieve ultra-narrow band perfect absorbers in near-infrared and mid-infrared regime,which can be widely applied in sensors,detectors,filters and thermal emitters.