Study On Plasmonic Metal-dielectric-metal Metamaterials Based Absorbers

Surface Plasmon?SPs?are the collective oscillations of free electrons and the propagation of electromagnetic waves at the metal dielectric interface.SPs can break the confinement of diffraction limit in traditional optics and be capable of a powerful local electromagnetic field enhancement effect.Due to the unique electromagnetic properties of SPs,they have shown great application prospects in the fields of energy,bio-medicine,and information.The metamaterial is based on metal-dielectric-metal structure,which can confine the height of the light field in the micro-cavity of the intermediate dielectric layer,and can achieve perfect absorption of wide bands and narrow bands in a specific frequency range.What'more,the advantages of high integration,small size,and low cost of metamaterials devices have been widely used in solar cells,bio-sensors.In this thesis,it introduces the mechanism of SPs and a metal-dielectric-metal metamaterial absorber based on SPs.This absorber has a good absorption effect in the ultraviolet-visible-near infrared band.Through the research of the absorber's structure design,optical characteristics and physical mechanism,further exploration of its application in solar cell sensing can be expected.The thesis specifically includes the following aspects:1.Introduce the surface plasmon,dispersion relations,and excitation methods,as well as two frequently-used numerical simulation methods for calculating electromagnetic waves,the finite element method?FEM?and the finite-difference time-domain method?FDTD?.The design of the metamaterial absorber in this paper mainly employs the finite-difference time-domain method to simulate the structure.2.An absorber is designed via a composite metal-dielectric-metal three-band metamaterial structure composed of an Au ring and a triangular prism Cr.The absorber is numerically simulated using a finite-difference time-domain method.The structure has broadband absorption with a rate exceeding 92%in the ultraviolet-visible light band,and narrow-band absorption with an absorption rate of98.5%at a near-infrared wavelength of 854nm.It also analyzes the physical mechanism of the absorber by calculating distribution of the structure electromagnetic field to change its structural parameters,effectively adjusting absorption spectrum to obtain enhanced optical absorption performance.It has a wide range of applications in integrated equipment,integrating solar photo-voltaic and sensors.3.Based on the above studies and numerical simulations,we have designed another ultra-wideband solar absorber metamaterial structure with SiO₂-Ti-SiO₂-TiN four-layer split-ring resonator.Under normal incidence conditions,the simulation results show near-perfect absorption of light waves with a bandwidth of 1182 nm in the range of 400-1582 nm.The absorption rates are all above 90%,and the average absorption rate is 97.8%.In addition,the absorber is insensitive to the polarization direction of polarized light,insensitive to the angle of incidence,simple in structure,which has many outstanding advantages,and has great application value in the field of solar absorbers.