Research On Analogue Of Electromagnetically Induced Transparency Phenomenon And Its Applications Base On Metasurface

The light wave is a kind of electromagnetic wave,which can be used in communication,sensing,detection and other fields.It is of great significance to regulate it effectively for the development of human society.Fano resonance can significantly enhance the interaction between light and matter,so it is widely used in the design of optical sensing equipment,optical switches and slow light devices.Analogue of electromagnetic induced transparency(EIT-like)is a special type of Fano linear,and the method of Fano resonance is also applicable to EITs.The difference is that EIT-like has a unique slow light effect,so it can be applied to the design of optical cache devices,improve the efficiency of optical communication.Conventional optical devices were bulky,expensive and difficult to manufacture.Metasurface devices not only have the characteristics of high integration,high performance,but also have the ability of flexible optical response,which has become one of the mainstream research directions.In the Fano resonances of metasurface devices,metal metasurface usually have higher sensitivity,but the inherent loss of the metal material causes the low Q factor.All-dielectric material makes up for the disadvantage of metal loss,and it can achieve higher Q factor,so it is widely used.Based on this,we used silicon material to design two excellent metasurface structures in this paper,respectively named M-like metasurface and hollow cylinder tetramer metasurface,which can realize EIT-like linear.We conduct electromagnetic field analysis and multipole decomposition of EIT-like,explored its formation mechanism,calculated its sensing and slow light performance,and explored its potential applications.Specific research contents are as follows:(1)M-like metasurface can excite an EIT-like peak,and through electromagnetic field analysis and multipole decomposition,it is concluded that the electromagnetic field distribution of such EIT-like is dominated by magnetic dipole mode.When exploring the formation mechanism of EIT-like,we observed the electromagnetic field distribution when horizontal silicon rods and three vertical silicon rods were separately placed in the cell structure.According to the distribution of electromagnetic fields,it can be seen that horizontal silicon rods can be directly excited by incident electromagnetic waves and act as a bright mode.The three vertical silicon bars cannot be excited directly by the incident wave,but they can be excited indirectly by bright mode and act as dark mode.So this type of EIT-like is formed by coupling of bright mode and dark mode.According to the relationship diagram between phase and wavelength of EIT-like,it is found that phase transition occurs in the vicinity of transparent window.The group delay formula is used to calculate the phase transition position with 0.16ps group delay,which confirms the slow light characteristics of this kind of EIT-like.At the same time,when the polarization angle of incident wave is changed,the transmission spectrum shows that the EITlike are more sensitive to the change,which can be used in the design of polarization sensitive devices such as optical switches.In terms of sensing performance,the Q factor is 152.3,the sensitivity is 250 nm/RIU,and the FOM value is 41.6RIU-1.In terms of slow light performance,this EIT-like has a group delay of 0.16ps.(2)Two Fano resonances dominated by magnetic dipole and toroidal dipole can be excited by a hollow cylinder tetamer metasurface in the symmetric case that the four hollow rings have the same radius of the etched-hole.By using the theory of Bound states In Continuum(BIC)to change the radius of the upper and lower rows of etched holes,the symmetry of the unit resonator in the X-axis direction is broken,and the radiation channel is constructed to transform the ideal BIC into the quasiBIC state.And it excites an EIT-like resonance in the transmission spectrum.At the same time,we also verified the inverse square relationship between the Q factor and the degree of asymmetry.The electric quadrupole is a high-order dipole,and its electromagnetic field distribution in space is more three-dimensional,which is not easy to identify only from the electromagnetic field diagram.Therefore,the multipole decomposition method is used to further confirm that the electromagnetic field distribution of this type of EIT-like is dominated by the electric quadrupole pattern.When exploring the formation mechanism of this kind of EIT-like,the distance between the four hollow cylinders in the unit structure is changed and it is found that when the distance increases,the EIT-like gradually separate into two Fano resonance.Through multipole decomposition,it is concluded that the two Fano resonances are dominated by electric quadrupole and magnetic dipole respectively,indicating that this kind of EIT-like resonance is formed by the coupling of two Fano resonances and finally presents a higher order electric quadrupole mode,which belongs to the coupling formation of two bright mode.When investigating the effect of polarization angle on resonance,it is found that the symmetric structure of the model is insensitive to the polarization of the light source,but the asymmetric structure is very sensitive.In terms of sensing performance,the Q factors of the three resonators are 1878.61,5653.4 and 678.42,and the sensitivities are 290nm/RIU,175nm/RIU and 430nm/RIU,respectively.The FOM values can reach 483 RIU-1,350 RIU-1 and 165 RIU-1,respectively.In terms of slow light performance,this class of EIT has a group delay of 2.75ps.In summary,the structure can support a variety of high-order Mie resonances and has a rich optical field limiting pattern.It can be used in the design of slow light devices and high-performance sensors,which is of great research value.