Dynamically Tunable Resonant Metasurfac

In recent years,metamaterials have developed into an emerging research hotspot across the fields of physics,chemistry,biology and medicine.Metasurfaces are used to achieve phenomena such as negative refraction,Fano resonance,stealth,plasmon light field manipulation,and optical activity.Its appearance has attracted widespread attention from many scholars around the world.Different from the traditional electromagnetic wave control device,it has the disadvantages of large size and high loss,because it controls the propagation principle of electromagnetic waves through the accumulated phase difference in the electromagnetic wave propagation process,and it is difficult to achieve miniaturization and customization.In view of this,metamaterials offer researchers a great deal of freedom to achieve the desired properties by changing the shape,material,and cycle of the structural units.The metasurface derived from the two-dimensional metamaterial has the characteristics of simple preparation process,easy excitation,flexible and rich regulation mode,etc.However,the resonant artificial metal metasurface still faces problems such as low conversion rate and large intrinsic loss,which is far from meeting the usual needs.In this paper,we study two kinds of resonant dielectric metasurface and metal-dielectric metasurface,combine phase change materials and two-dimensional materials through simulation design,principle analysis and structural optimization,and apply them to light modulation such as improving dielectric quality factors,resonance regulation and light absorption enhancement.The main research contents of this paper are as follows:（1）Active optical modulation breaks the limitations of passive devices and provides a completely new alternative to enabling high-performance optics.The phase change material vanadium dioxide（VO₂）plays an important role in the regulation of active devices due to its unique characteristics.We first study the optical modulation of Si-VO₂ resonant hybrid metasurfaces,and the designed dimeric nanorod metasurfaces can excite bound state-quasi-BICs modes in a continuum.And by rotating one of the nanorods,the quasi-BICs resonator can have a high mass factor.Calculating the multipole decomposition and simulating the near-field distribution from the data confirms that it is mainly magnetic dipoles that dominate this resonance.Next,to achieve dynamic tunable of the metasurface,we integrate VO₂ films into the Si nanostructures of these quasi-BICs.With the increase of temperature,VO₂gradually changes from the medium state to the metallic state,and with a significant change in optical response,the modulation law of the transmission spectrum is calculated.By comparing the transmission spectrum and modulation depth of VO₂ at different positions,a transmittance modulation ratio of up to 180%was achieved.These results fully confirm the excellent modulation ability of VO₂ thin film alignment BICs resonators.Our work provides a new route for modulation of resonant optics.（2）Graphene is regarded as a supermaterial in the twenty-first world,because its two-dimensional structural properties and zero-band gap band structure allow surface plasmons to be excited and propagated,giving people unparalleled ability to manipulate light.We designed an actively tunable surface plasmon-enhanced light absorption device using a variety of graphene metamaterials.We first integrate graphene with light-absorbing materials（semiconductors and two-dimensional materials）to form a hybrid periodic array metasurface structure.By changing the graphene Fermi level,the properties of the incident light,and the polarization direction of the incident light,we achieve multi-wavelength light restriction and absorption enhancement regulation.Through simulation calculations,it is confirmed that the graphene-dielectric hybrid metasurface has strong electric field binding ability and large resonance modulation range.This metasurface provides an important theoretical basis for the further development of electromagnetic wave control devices based on this design.