Study On Optical Property Of Ultra-wide Band Mid-infrared Meta-materials Absorber

Electromagnetic metamaterials are composite materials that rely on artificial structures to achieve extraordinary electromagnetic responses.The extraordinary electromagnetic properties of metamaterials are not only related to the properties of the materials,but also to the shape of the artificial structure,the size of the structure,and the arrangement of the structure.Therefore,the design of the electromagnetic metamaterial is very flexible.Due to the dual advantages of design and properties of electromagnetic metamaterial absorbers,they have been widely studied in microwave,terahertz,near infrared and visible light bands.Among them,infrared metamaterial absorbers have a very broad development prospect and huge application potential in infrared detection technology,infrared imaging,and infrared.Stealth,thermal photovoltaics,solar cells,and sensitive detection.In recent years,it has quickly become a research hotspot in the field of artificial electromagnetic structural materials.With the development of research,the bandwidth problem of electromagnetic metamaterial absorbers has caused widespread concern.Due to the resonance characteristics of the electromagnetic metamaterial absorber,its absorption frequency is closely related to its structure,showing that most structures are narrow-band absorption.So far,many research teams at home and abroad have proposed various broadband mid-infrared metamaterial absorbers.The main method adopted is to combine unit structures of different sizes in a periodic structure.According to the resonance characteristics of the structure,a unit structure of one size corresponds to one absorption peak,so the combination of multi-sized unit structures can generate an absorption band.This method can effectively expand the bandwidth,but the bandwidth after expansion is still insufficient,and the average absorptivity still has room for improvement;and the absorbers with multi-size patterned structure increases the complexity and difficulty of the preparation process.Therefore,using a single-sized patterned structure to achieve an absorber with ultra-broadband,high-absorptionbecome the focus and difficulty of research.Based on the propagation surface plasmon(PSP)resonance and local surface plasmon(LSP)resonance in electromagnetic metamaterials,in the mid-infrared band,we design a single-sized patterned absorber.The structure consists of four layers,reflective metal Ti,dielectric layer SiO2,thin Ti layer,and top patterned Ti(Ti patch of the same size),namely Ti/ SiO2 / Ti / Ti patch structure.The absorption performance was studied by numerical simulation in the mid-infrared band.The idea of introducing multi-frequency resonance was adopted to make the absorber achieve near-perfect broadband absorption in the infrared window of the atmosphere.The maximum absorption in the wavelength range of 9.77 ?m to10.69 ?m is as high as 99%.The average absorption in the mid-infrared band of 8 ?m to 13?m can reach 96.7%.Secondly,we studied the influence of structural parameters in the absorber on the absorption performance.The results show that the thin Ti film promotes both the PSP resonance and the LSP resonance.In the window of the atmosphere,the absorption performance is excellent when the thickness of the thin Ti film is within 0.001 ?m to 0.005?m,which provides an allowable error range for the thickness of the thin Ti film for the experiment.When the size w of the patch Ti is increased from 1.1 ?m to 2.1 ?m,the absorbance of the absorber in the mid-infrared band is gradually increasing,and the absorption bandwidth is gradually widening.When the w value is increased from 2.4 ?m to3.3 ?m,the absorptivity of the absorption spectrum gradually decreases,and the absorption bandwidth also becomes unsatisfactory.When the thickness of the Ti patch is less than 1.9 ?m,the absorption band of this structure is mainly concentrated in the short-wavelength region of the mid-infrared band.However,when the thickness of the Ti block is greater than 1.9 ?m,the absorption band of the absorber moves significantly in the long wave direction.The gap between adjacent Ti patchs have a large effect on the absorption bandwidth.When the gap is small,the two absorption peaks of the absorber are more obvious and the absorption band is wider.When the angle of incident light is increased from 0 ° to 30 °,the band width and absorptivity of the absorber remain almost unchanged,that is,the absorber has relatively stable absorption performance within the angle of incident light of 30 °.The results of this paper provide a meaningful reference for the experimental preparation of broadband metamaterial absorbers in the mid-infrared band.