Research Of Electromagnetic Induced Transparency-Like Phenomenon Based On Silver Nanostructures

Electromagnetically induced transparency(EIT)initially refers to a phenomenon that occurs in a three-level atomic system.The reason for this phenomenon is that the destructive interference of the energy level in the system occurs between two transition channels.The result is that there is a clear transmission peak in the spectrum without transmission,that is,the generation of a transparent window,and some documents call it electromagnetically induced transparency.The traditional EIT effect implementation is subject to experimental conditions,such as the need for a stable gas laser and ultra-low temperature environment during the experiment.Later,people found that metamaterials and nanostructures can also produce electromagnetic-like transparent phenomena.The realization of electromagnetic induced transparency based on metamaterials and nano structures has become a research hotspot in recent years,because it is in nanostructures or metamaterials.Strict experimental conditions may not be required,and this discovery is called an electromagnetically induced transparency-like(EIT-like)phenomenon.If the electromagnetically induced transparency phenomenon is based on the plasmon effect of the precious metal structure,this electromagnetically induced transparency phenomenon is called the Plasmon Induced Transparency(PIT)phenomenon.In recent years,in nanophotonics,due to the plasma nanostructure,a large electric field intensity can be generated in a small area.Therefore,the combination of EIT and nanoplasmon structure provides a new way to reproduce the surface plasmon induced transparency phenomenon in atomic systems.In this paper,first of all,we innovatively propose a simple structure that can achieve double transparent windows.This structure has a narrow and wide transparent window at the near infrared wavelength of 790.79 nm and near 1100 nm under the normal incidence of the light source.The wider transparent window can realize the transmission of more than 80% of the wavelength of 906 nm to 1147 nm.The transparent window can be controlled by adjusting the structural parameters of the orthogonal rectangular silver nanoarray.In this paper,a numerical study of orthogonal rectangular silver nanostructures with multiple transparent windows is carried out.The structure of the design is very simple.It consists of a silver nano-antenna placed horizontally and a silver nano-antenna placed vertically on a silicon dioxide substrate.The two transparent windows in the proposed nanostructure are formed by indirect coupling of two bright modes.The transmission spectrum curve of the orthogonalrectangular silver nanostructure is calculated by the numerical method finite difference time domain(FDTD).There are three transmission peaks and valleys in the transmission curve.The absorption and reflection at the peak and valley are as high as 99.9%,which can be used in the design of specific wavelength filters.In addition,we also simulated the sensing performance of the three resonance peaks of the structure.The highest refractive index sensitivity is 608nm/RIU.The two transparent windows in the transmission spectrum can also be used to detect the refractive index sensor..On the other hand,we analyzed the slow light effect of the structure,deduced the electromagnetically induced transparency-like linear coupling formula,and introduced the magnetic permeability,which can be derived from the magnetic susceptibility formula.Whether the dispersion of group velocity occurs is determined by the real part of the polarizability.This directly leads to the occurrence of the slow light effect,and the loss is related to the imaginary part of the polarizability,so the transmission peak of electromagnetically induced transparency-like will appear when the loss is low.We calculated the loss through absorption.The simulated absorption spectrum and the theoretical formula calculated results are basically the same.Then we derived the group refractive index formula.The derivation proves that we can approximate the group refractive index through the phase slope calculation,such as the derivation formula.,Calculated that the group refractive index reaches the maximum at 790.79 nm,the maximum group refractive index is192.3.It is verified that this structure has certain application value in slow light effect.The double transparent window based on the electromagnetically induced transparency-like phenomenon is simple in structure and small in size,and is expected to be used in sensing,dual-band absorption,slow-light devices and other equipment.Finally,the full text of the work is summarized,and the future work is prospected.The future work will be dedicated to the design of a structure that can achieve tunable electromagnetically induced transparency-like.