Electrically Controlled Optical Properties In Metamaterials Based On Epsilon-near-zero Materials

In 2001,the concept of metamaterials was introduced by Professor Walse.Metamaterials are materials that are created by human design and are different from natural materials through the orderly and hierarchical division of structures to modulate physical properties.Unlike common materials,metamaterials have unusual and extraordinary physical properties.These extraordinary properties have nothing to do with the material itself,but rather with the artificially designed structure.Current research interests such as artificially intelligent metasurfaces,quantum metamaterials,electromagnetic metamaterials,as well as the well-known photonic crystals,electromagnetic crystals and artificial magnetic conductors all belong to the category of metamaterials.The existence of metamaterials provides a good avenue for future technological development.Transparent Conductive Oxides(TCOs)are used in a wide range of applications in solar cells,transistors and flexible electronics.Photonic structures and devices based on TCOs have also been investigated in the last few years.electric gate control structures using TCOs as active elements were first proposed and demonstrated by Feigenbaum et al.Dielectric constant tunability was investigated through the accumulation of free carriers between metal-oxide heterostructures and Indium Tin Oxide(ITO)layers.Indium Tin Oxide(ITO)is an excellent TCO material with a low resistivity,a transparent state in the visible range and a high reflectivity to infrared light.Indium tin oxide is not only a more desirable material for energy efficiency,but also an excellent material for transparent electrodes.Based on semiconductor doping theory,the dielectric constant of ITO is regulated by electron doping the ITO so that the real part of the dielectric constant changes from positive to negative in the near infrared region,implying the appearance of a dielectric constant zero point in this range of change.From Maxwell’s set of equations,it is clear that the convergence of the dielectric constant to zero is accompanied by the appearance of a number of novel optical phenomena.To further investigate the properties and phenomena of materials when the dielectric constant is near zero,the dielectric constant near zero(Epsilon-near-zero,ENZ)is defined when the absolute value of the real part of the dielectric constant is less than one.Materials with this property are also defined as having near-zero dielectric constants.With the continuous development of ENZ theory research,researchers have proposed many novel photonic devices and realised the application of ENZ materials in different fields,demonstrating that the photonic properties of ENZ have a broad application prospect in the fabrication of highly integrated and high performance chips.In this paper,a class of MOS-structured superconfigurable materials(Matematerials)is designed using the ENZ properties of ITO,and the function of electronically controlling the optical properties of superconfigurable materials is achieved through electron doping.The metal-oxide-semiconductor in the MOS structure is made of a cube with length and width p and thicknesses h1,h2 and h3.An open square metal ring with outer ring size a,inner ring size b and opening width d and thickness h4 is added to the MOS structure.The effect of the structural parameters h1,h2,h3,p and h4,a and b on the reflectivity of the MOS-like structure is investigated to obtain the effect of the structural parameters on the reflectivity and to achieve the regulation of the reflectivity in the near-zero region of the dielectric constant.When the material Ag is chosen for the substrate metal layer and the metal ring layer,the reflectance valley can be regulated in the ENZ region of the ITO.Therefore,the variation of the reflection valley in the region of near zero dielectric constant is investigated for different bias voltages.From the results,the reflection valley moves and changes within the region of near-zero dielectric constant at external bias voltages from 0V to 3V,achieving the function of electrically controlling the optical properties at near-zero dielectric constants.A new foundation for future communications,imaging and sensing is laid.