Study Of A New Type Metasurface For High Sensitive Sensors

Metamaterials and metasurfaces demonstrate unique electromagnetic features that can effectively control the polarization and phase of electromagnetic waves.More and more researchers are interest in the metasurfaces to apply them for developing highsensitivity sensors designs.It has a great potential and good application prospects.Metasurfaces can enhance the interaction with linear and nonlinear media,reduce the size of the device and increase the degree of localization of the electromagnetic field.However,in near-infrared and visible parts of spectrum,the metallic-inclusion-based metasurfaces often face the application obstacles associated with using expensive noble metals and high Ohmic losses in them.A possible solution of that is to use all-dielectric structures instead of metallic ones.In the other hand,in optical range,one of the important factors for applied devices is the radiation energy loss.For reducing and controlling radiation losses,it has been proposed to make an all-dielectric metasurface consisting of resonators,which support a special type of resonance called the Trapped mode and also known as the Dark mode or the Bound State in a Continuum.This paper presents comprehensive study of all-dielectric metasurfaces supporting the excitation of trapped mode and discusses the feasibility of applying them in sensor devices.First.The basic design of a metasurface that supports excitation of low-Q electric and magnetic resonances is studied simultaneously with the design that supports excitation of the high-Q trapped mode.The resonances are excited by linearly polarized incident wave.The metasurface that supports trapped mode excitation is an array with unit cell in the form of a single subwavelength dielectric disk with a round eccentric penetrating hole.Resonant states in the transmitted spectra of the metasurface are identified from the comparison with modes inherent in the individual cylindrical dielectric resonators.Correlation between an asymmetry in the geometry of unit cell and formation of the high-Q trapped mode is established.Second.The design of the polarization-insensitive metasurfaces is studied.For this metasurface,it is utilized the same disk resonator with an eccentric hole,combined with the group theory.The unit cell of the metasurface is composed of four dielectric disk resonators,which are combined together in the form of a symmetric C4 rotating group(C4 group design).Third.In order to further study,the influence of the asymmetry on characteristics of electromagnetic waves for design of polarization insensitive metasurfaces(unit cell with C4 v group symmetry)is demonstrated.As a result,for this metasurface,the trapped mode can be excited with strong and homogeneous electric near-field,which is distributed in-plane of the structure and is localized outside the high-refractive-index dielectric resonators.Fourth.The effect of the dielectric constant of the substrate on the resonance frequency of the trapped mode is studied.Fifth.The experimental prototype of the refractive index sensor is fabricated and an experimental characterization is performed in the microwave frequency range.Thus,the presented researches demonstrate perspectives to use all-dielectric materials instead of metal ones to make a metasurface for sensor applications.This new generation of metasurfaces can be used in the design of refractive index sensors with high sensitivity.