Visible/Infrared Spectrum Matching Design And Control By Multiband Metamaterial Absorber

With the development of active/passive detection technology,the objects should have compatibility with different stealth methods.It is necessary to solve the contradictions between infrared stealth low emission and laser stealth high absorption,infrared stealth low emission and radiative heat dissipation high emission,and consider the selective absorption of atmospheric spectrum for objects in atmosphere.Considering four elements of objects,environment,detection mode and radiation heat dissipation,it is necessary to meet the harsh requirements of low emission in detection band,high emission in non-detection band,high and ultra-narrow absorption of laser band,and dynamic controllability for the laser/infrared compatible stealth in atmosphere.The research progress of multiband metamaterial absorber provides a potential method to solve the above problem.This thesis mainly focuses on the spectral matching design by multiband metamaterial absorber and application in stealth and camouflage.Develop methods to control the number,bandwidth,frequency,and absorptivity of absorption bands for the design ability of spectral absorption characteristics of the multiband metamaterial absorber by studying the excitation and enhancement mechanism of resonance modes of metal and dielectric structures.For the different requirements of optical stealth camouflage applications,design corresponding absorption and reflection spectrum and provide supports for objects'surface spectrum design and control.Some higher-order modes have the problems of difficult excitation,low absorptivity and poor availability in designing multiband metamaterial absorbers.So it is firstly studied that the excitation and enhancement mechanism of magnetic plasmon resonance modes of metallic square resonators in this thesis.Numerical simulation study shows that the absorptivity of MP_1,2 mode is very low and its local electromagnetic field concentration ability is significantly weaker than the high absorption modes MP_1,0 and MP_3,0.Strong near-field coupling between the electromagnetic fields accumulated at the tips is produced by rotating square resonators to enhance the local electromagnetic field concentration and absorptivity of MP_1,2 mode.The experimental samples are fabricated and tested by infrared microspectrometer.The results show that the tip-tip coupling configuration can enhance the absorptivity of high-order MP_1,2 mode by 4.5 times.Theoretical analysis of the electromagnetic field distribution characteristics is carried out to find the underlying physical mechanism of absorptivity enhancement.It is found that the tip-tip coupling configuration can enhance the electric field intensity of MP_1,2 by 13 times.Based on the symmetry breaking idea in transmission metasurface,magnetic plasmon resonance MP_1,1 mode is excited by breaking the symmetry of square resonators.Based on the excitation and enhancement mechanism of the metallic square resonators,this thesis study the enhancement mechanism of high-order MP_1,2 modes of metallic square ring resonators and design method of multiband metamaterial absorber.Numerical simulation studies firstly find that the electromagnetic field distribution of the MP_1,2 mode has similarities and differences between square ring resonators and square resonators.It is accumulated around the four tips and it is also concentrated in the interior of the structure.For the distribution similarities,tip-tip coupling configuration is introduced into the structure design of metallic square ring resonators to enhance absorptivity.For the distribution differences,enhancement configuration is designed based on the near-field coupling effect,proposing the outer-square-inner-strip coupling configuration and outer-square-inner-disk configuration to enhance the higher-order MP_1,2 mode.An eight-band metamaterial absorber is achieved by combining two different sized outer-square-inner-strip structure with average absorptivity 0.94.Excitation and enhancement mechanism of silicon square structure is studied by using high dielectric constant,low loss and thermo-optical characteristics of silicon material to design multi-ultranarrow-band metamaterial absorber and satisfy the ultranarrow and dynamic control requirements in laser stealth.The electromagnetic field distribution of silicon square is firstly analyzed.Coupling configuration and asymmetric configuration are proposed based on the ideas of near-field coupling and symmetry breaking in the high-order mode enhancement of metallic resonators,which can excites high-order toroidal dipole and toroidal quadrupole.A four band ultranarrow metamaterial absorber is achieved with average bandwidth nine nanometers based on the newly proposed high-order modes enhancement configuration.The study of temperature dynamic characteristic shows that the high-order magnetic toroidal dipole mode has the narrowest absorption band,the highest quality factor,and the best thermo-optical control characteristic.For different requirements of optical stealth and camouflage,absorption,emission,and reflection spectrum matching study is carried out by multiband metamaterial absorbers based on the resonance modes with different spectral absorption characteristics.Based on the study of excitation and enhancement mechanism of MP_1,2magnetic resonance mode,a multi-functional metasurface is obtained with low emission in the atmospheric window area and high emission in the water vapor absorption band to fulfill the needs of infrared stealth and heat dissipation.A single,ultranarrow,and thermally tunable metamaterial absorber is designed for the spectrum matching and dynamic control of laser stealth utilizing the higher-order magnetic toroidal dipole excited by the 2-D four-silicon-square coupling configuration:absorptivity 0.97 at laser wavelength 1064nm,bandwidth 1.4 nm,and thermo-optic modulation depth up to 0.82.The asymmetric structure is adopted to obtain multiband metamaterial absorbers with polarization sensitive absorptivity and center frequency.The absorption characteristics are used to control the RGB components of the reflection spectrum to satisfy requirements of optical camouflage.In addition,spectrum matching design of laser/infrared compatible stealth technology is developed with multiband metamaterial absorber based on fundamental modes of the complex 3-D all metal composite structure.