Design And Analysis Of Infrared Metamaterials Based On RCWA

Metamaterials have extraordinary physical properties not found in traditional materials.In recent years,with the continuous development of micro-nano processing technology,the working frequency of metamaterials has been continuously improved.Therefore,the research of metamaterials has received a lot of attention in the infrared band,especially for the infrared absorbing metamaterials,which have the characteristics of broadband/flexible design and thus can be appliced in the fields of sensors,infrared detection and radiation control.In this paper,we use the Rigorous Coupled Wave Analysis approach to explore the electromagnetic absorption characteristics of the magnetic resonance modes and epsilon near zero（ENZ）properties in metal-insulator-metal（MIM）grating structures.The main research work is as following:（1）Through simulation and experiment to study the electromagnetic response of the SiO₂-Al double-layer structure in different polarization modes（TE polarization and TM polarization）and different incident angles,verified that the excitation conditions for perfect absorption of ENZ mode in TM polarization and obliquely incident.The absorption efficiency is close to 100%of the double-layer structure near the ENZ point（λ=8μm）,and this absorption mode has the characteristics of sub-wavelength field enhancement and field localization.Further study effect of the structural parameters and the surface metal grating layer on the ENZ mode,which revealed that the presence of strong dielectric loss of the SiO₂ film atλ=9.5μm will suppress the ENZ mode.The comparison and verification reveals that the mian factor that excites the ENZ mode is the component electric field perpendicular to the incident interface of the ENZ layer.（2）To study the influence of the magnetic resonance mode on the ENZ mode,by designing the Al-SiO₂-MgF₂-Al square grating structure,the magnetic resonance mode in the structure was used to successfully excite the ENZ mode under normal incidence and break the existence of the ENZ mode such as polarization sensitivity and angle dependence.The effects of structural parameters on the coupling of ENZ mode and the magnetic resonance are explored.Based on the equivalent dielectric theory and the electric field distribution in different dielectric layers,the dielectric layer MgF₂ film thickness affects the coupling of different absorption modes.Combining the near-absorption peak generated by the coupling between magnetic resonance and ENZ mode,and the loss absorption of the SiO2 film at a wavelength ofλ=9.5μm,a multiple absorption modes was realized and experimentally verified.Finally,result in a 90%broadband absorption at the infrared wavelength range of 7.8¹0.2μm.（3）For the MIM grating structure,the effect of different structural parameters on the magnetic resonance behavior was studied using equivalent media theory,and it was found that the width of the metal grating can effectively control the resonance wavelength of the magnetic resonance.The studies have shown that the surface wave（surface plasmon polarizations）generated at the interface between the surface periodic metal layer and air of the MIM grating structure will couple with magnetic resonance in a certain wavelength range,which suppress the absorption of magnetic resonance modes.In the strong coupling state,the magnetic resonance absorption bandwidth becomes narrow.