Research On Broadband Infrared Metamaterial Absorbers Based On Coupling Plasmon Resonances

As a synthetic material,metamaterials can achieve optical properties that are difficult to achieve in nature through artificial regulation,and have become an important research direction in recent years.The unique plasmon resonance of metamaterials can realize the regulation of the amplitude,phase and polarization of the incident electromagnetic wave,and even realize the interaction of light and matter in more dimensions.Metamaterial absorber is a hot branch in the field of metamaterial research,compared with the traditional electromagnetic absorbing structure thickness is at least a quarter of the incident light wavelength,metamaterial absorber can achieve perfect absorption of incident light while making its own structural thickness much smaller than the incident light wavelength.As absorbers,metamaterial absorbers can be widely used in solar cells,satellite bolometers,light detectors,and spectral imaging.In addition,combining metamaterial absorbers with pixels from uncooled infrared detectors and microbolometers can achieve thinner thicknesses as well as higher absorption rates,thereby reducing noise-equivalent temperature differences.Plasmon resonance-based metamaterial absorbers have near-field enhancement characteristics,and through the flexible selection and adjustment of materials and sizes,the ideal absorption effect can be achieved for incident light in any target band.Based on the surface plasmon resonance and the properties of metal and dielectric materials,this paper proposes and designs some absorbers with small size and easy configurations to make for the absorption coating of uncooled infrared detectors,and designs and optimizes its structural parameters to achieve broadband high absorption in the target band（long-wave-very-longwave infrared）,the specific research work is as follows:1.The working principle of metamaterial absorber was explored,and a theoretical method to enhance infrared absorption was established.Based on the research on propagation and local surface plasmon excitation and high-loss materials,a variety of metamaterial absorber structures are designed to achieve broadband high absorption of target long-wave infrared,and the advantages and disadvantages of inert metals and high-loss metals as metal layers are analyzed,and a complete design scheme of broadband metamaterial absorbers is obtained.2.According to the principle of multi-mode local surface plasmon resonance to enhance broadband absorption,two coplanar and laminated metamaterial absorber structures,W/Si/Ti and W/Zn Te/W/Ge/W structures,are proposed,which can achieve broadband absorption of 8～12μm and 8～14μm,respectively.In addition,according to the study of the absorption curve after replacing different metal materials,it is found that inert metals have good wavelength selectivity for the absorption peaks of metamaterial absorbers,and inert metals with high refractive index are more suitable for fusing multiple resonance modes to form broadband absorption peaks than high-loss metals.3.Aiming at the problem that the structure design of absorber may be too complicated due to the wide wavelength range of long-wave infrared band,the structure of Ti/Ge/Ti metamaterial absorber based on high-loss metal resonance is proposed and experimentally verified,although high-loss metal does not have keen wavelength selectivity for plasmon resonance like inert metal,but it can excite wide-peak resonance,using this feature,you can rely on the design of only one resonant structure in the absorber unit,by adjusting the size parameters of each component of the metamaterial.A more ideal broadband absorption peak is obtained in the infrared band of the target.4.In order to achieve perfect broadband absorption in the entire long-wave infrared band,the dielectric layer components are adjusted,and a four-layer Ti/Ge/Si₃N₄/Ti absorber structure composed of loss-type medium and lossless medium is proposed,which realizes broadband high absorption of 8～14μm.Si3N4,a loss-type medium,has a refractive index imaginary term in the long-wave infrared band,which determines the intrinsic absorption of incident light,in addition,the loss-type medium has a regulatory effect on the two plasmon resonant modes,which increases the tunability of the absorber structure,effectively increases the overall bandwidth and absorption rate of the absorption curve,and achieves the effect that is difficult to achieve with a single lossless dielectric layer.According to this structural design,Ti/Si/Si O₂/Ti absorbers that can realize very long-wave infrared broadband absorption are proposed,and broadband absorption curves of 14～30μm and 8～30μm can be realized by adjusting the size,respectively,and realize broadband high absorption from the entire long-wave to the very long-wave infrared band.