| The infrared band occupies a very important position in the electromagnetic wave band.Studying the absorption characteristics of objects in the infrared band can promote the development of infrared detection technology,infrared stealth,infrared thermal imaging and other fields.Traditional infrared devices use the inherent characteristics of natural materials to realize the regulation of electromagnetic waves,but such devices have limited ability to regulate electromagnetic waves,resulting in problems such as narrow operating band and low absorption rate.Metamaterials can obtain extraordinary properties that are not possessed by natural materials through artificial design.Therefore,metamaterial-based absorbers provide a new approach to address the above problems.But so far,the absorbers working in the infrared band still have the shortcomings of not wide absorption band,and difficult to realize multi-parameter control of the structure.In view of the above shortcomings,based on the impedance matching theory and the absorption characteristics of the metal-dielectric-metal structure,an embedded long-wave infrared ultra-broadband perfect absorber and an ultra-broadband infrared absorber based on genetic algorithm-aided design are proposed.The difference method analyzes two different structures.The specific work of the paper is as follows:First,an embedded long-wave infrared ultra-broadband perfect absorber is designed by combining impedance matching theory and finite-difference time-domain method.Based on the metal-dielectric-metal structure,the absorber embeds the MIM structure into the intermediate dielectric layer to achieve near-perfect absorption in ultra-wideband.In the long-wave infrared region,the MIM structure induces the obtained Fabry-Perot cavity resonance and the localized surface plasmon resonance,and the synergistic effect of the propagating surface plasmon and the cavity membrane resonance together leads to the broadband perfect absorption of the embedded structure.The absorption performance of the structure is analyzed by the finite difference time domain method.Experiments show that the absorption rate of the embedded structure in the 7-14μm band is greater than 90%,the relative absorption bandwidth can reach 67%,and the average absorption rate is as high as 97.55%;and the absorber is insensitive to the polarization state and has large-angle absorption.excellent characteristics.At the same time,the influence of the physical parameters of the structure on the absorption spectrum is further studied,which provides a basis for the design of tunable absorption structures.This shows that the proposed embedded metamaterial absorber can achieve excellent absorption in the long-wave infrared wide-band range,and has certain reference value for the application of the absorber in thermal emitters,infrared sensors and other fields.Secondly,in order to further broaden the absorption band and find the optimal solution of the multi-parameter structure,a genetic algorithm is used to optimize the design of an ultra-broadband infrared absorber with a multilayer rectangular structure.The genetic algorithm takes the physical parameters of the multi-layer rectangular structure as the input,and the average absorption rate of the structure as the output of the fitness function.Through the simulation analysis of the optimal multilayer rectangular structure,the results show that the infrared absorber has an average absorption rate of 94% in the ultra-broadband range of3-14μm,among which the mid-wave infrared(3-5μm)and long-wave infrared(8-14μm),the average absorption rates of 94.9% and 94.2% are achieved,thus achieving the design goals of broadband and high absorption.The multilayer rectangular structure also exhibits arbitrary polarization independence and wide-angle absorption.In addition,the combined action of localized surface plasmon resonance,propagating surface plasmon resonance,and cavity mode resonance enables ultra-broadband high absorption properties.The two metamaterial absorbers based on the MIM structure designed in this paper have good absorption properties in the infrared band,and the absorber has a simple structure and small thickness,which is compatible with the lithography process,making it possible for mass production.In addition,algorithmic optimization aids the design of metamaterial absorber structures,which can reduce the time spent by traditional manual methods.This provides a reference for the design of metamaterial absorbers with excellent absorption performance in the future. |
