Optimization Design And Application Of Surface Plasmons Metamaterial Absorber

The nascent field of metamaterial has attracted significant attention on account of its exotic electromagnetic properties in recent 20 years.However,in most of the metamaterial devices,metal structures are most commonly used.In practical applications,the absorption losses are inevitable in metamaterials,which often degrades their performance.Hence,significant attentions have been paid to make devices with a low-loss performance.Some structures are presented to decrease the absorption losses by means of particular methods,for instance by optimizing structural geometries and by using gain materials.The concept of perfect absorption of metamaterial has initiated a new field of study,which made absorption loss an advantage.Therefore,in recent years,research on the perfect absorption of metamaterials(or metamaterial absorber)has also gained intense attention.Based on surface plasmon transmission and interaction and using the finite difference time domain method,our article deeply studied the mechanism and absorption characteristics in terahertz wave and mid-infrared region for the metamaterial absorber.The main work contents and results are as follows:We present a multi-band terahertz absorber formed by periodic square metallic ribbon with T-shaped gap and a metallic ground plane separated by a dielectric layer.It is demonstrated that absorption spectra of the proposed structure consist of four absorption peaks located at 1.12,2.49,3.45 and 3.91 THz with high absorption coefficients of 98.0%,98.9%,98.7% and 99.6%,respectively.It is demonstrated that the proposed absorber has the tunability from single-band to broadband by changing the length of square metallic ribbon and we can also select or tune the frequencies which we want to use by changing polarization angles.Importantly,the quality factor Q at 3.91 THz is 30.1,which is 5.6 times higher than that of 1.12 THz.These results indicate that the proposed absorber has a promising potential for devices,such as detection,sensing and imaging.We numerically investigate the optical performance of a periodically patterned Hshaped graphene arrays by the finite-difference time-domain(FDTD)in the midinfrared region.The simulated results reveal that absorption spectra of the proposed structure consist of two dramatic narrow-band perfect absorption peaks located at 6.3 ?m(Mode 1)and 8.6 ?m(Mode 2)with high absorption coefficients of 99.65%,99.80%,respectively.Two impressive absorption bandwidths which are the full width at half maximum of the resonant frequency(FWHM)of 90 nm and 188 nm are obtained.Dipole resonance mode is supported by graphene ribbon at wavelength of 6.3 ?m.While the other absorption,attributed to hybridized mode,is a new resonance which is different from the dipole resonance.The spectral position of the absorption peaks can be dynamically tuned by controlling the refractive index of the dielectric and the Fermi energy of graphene.Furthermore,we can obtain multi-spectral absorption peaks by applying multilayer graphene arrays.These design approaches enable us to control the number of absorption spectrum and such absorbers will benefit the easy-to-fabricate nano-photonics devices for optical filtering,thermal detectors and electromagnetic wave energy storage.We present an active,polarization independent plasmonic device based on graphene.To achieve highly confinement of the graphene surface plasmons,we use a silicon diffraction grating underneath the monolayer graphene backed a metallic ground plane.Dramatic absorption peaks are realized by using the finite-difference timedomain(FDTD)simulations.This structure can be used as a highly tunable optical modulator due to its precise control by varying the Fermi energy of graphene.Furthermore,we obtain multi-spectral absorption peaks by changing the period and the radius of silicon.In this paper,we present the absorber not only using a lossless metallic mirror,but also a multilayer Bragg mirror.Under these two conditions,we can obtain the high absorption.Such absorbers will benefit the easy-to-fabricate devices for thermal detectors,optical modulator and electromagnetic wave energy storage.