Simulation Study Of Broadband Mid-infrared Absorber Based On HBN Material

In recent years,the development of electromagnetic wave absorbers has made great progress.The reason for its absorption is basically caused by various forms of resonance: surface plasmon resonance,magneton resonance,Fabry-Perot resonance cavity resonance,and so on.As long as the incident electromagnetic waves meet the resonance matching conditions,the absorber can achieve a strong absorption effect.Magnetron resonance is a common resonance effect: it is mainly aimed at electromagnetic wave absorbers with a metal(metal-like)/ dielectric / metal(metal-like)three-layer structure(MIM).For this structure,the middle dielectric layer often needs to have a positive dielectric constant,while the top and bottom metal(metal-like)layers need to have a negative dielectric constant in a specific band,so that the magnetron can be excited.When the incident electromagnetic wave satisfies the matching conditions of resonance,a strong absorption effect can be produced at the resonance wavelength.In the mid-infrared band,h BN materials can exhibit metalloid effects in a specific band,so they have high application value.In the beginning of this article,we introduced some basic theoretical knowledge: surface plasmon effect and magneton resonance effect.Next,we introduced the current development status of electromagnetic wave absorbers,and prepared for the next research work.Then we detailed the numerical simulation method used in this paper,and designed two mid-infrared electromagnetic wave absorbers based on h BN materials based on theoretical knowledge.At the same time,we also introduced the basic characteristics of the materials(h BN,Ag).The absorption characteristics of the two designed mid-infrared absorbers combined with the field distribution are explained in detail,and the relationship between the absorption characteristics and structural parameters of the designed absorbers is studied in order to obtainthe optimal structure parameter.The specific work is as follows:(1)A cone-shaped mid-infrared absorber based on hexagonal boron nitride was designed.This is a grating-type absorber whose absorption mechanism is the magneton resonance effect and the Fabry-Perot cavity resonance effect.The influence of the structure parameters,operating wavelength and incident angle of the absorber on its absorption performance was analyzed using a finite element algorithm.The results show that under the optimized structural parameters,the absorption rate of the absorber can reach 80% or higher at an incident wavelength of 5.6 to 14.5 microns and an incident angle of 0 to 75 degrees.(2)A multi-groove-type mid-infrared absorber coated with a hexagonal boron nitride material was designed.This is a grating-type absorber.The unit structure includes multiple air grooves dug out of the dielectric.The sides and bottom of the groove are evenly coated with hexagonal boron nitride material,and the depth of the groove is linearly graded.The absorption characteristics of the absorber are caused by the combined effect of the surface plasmon resonance effect and the dielectric cavity resonance effect.The effects of structural parameters,working wavelength and incident angle on the absorption performance of the absorber were studied using a finite element algorithm.The results show that under the optimized structural parameters,the absorbance of the absorber can reach 90% in the wavelength range of 5.5to 15 microns and the range of incident angles of 0 to 75 degrees,And greatly widened the absorption bandwidth of the absorber.The research in this article paves the way for the design and application of mid-infrared absorbers to a certain extent.