Research On Optical Delay Unidirectional Waveguide Of Magnetic Photonic Crystal

All-optical network is the development direction of next-generation network.The processing of all-optical signal requires continuous improvement of the storage and conversion capabilities of optical pulses,and optical delay.The research on how to control the propagation speed of light waves becomes a hot research domain.Optical delay technology has important applications in future network and is a key technology for realizing all-optical communications.Photonic crystals have the advantages of tiny structures,high controllability,low loss,and band gap structure,and exhibit great advantages in realizing optical delay.In this paper,photonic crystal waveguide and optical delay technology are combined to achieve optical delay in two different ways,including reducing the group velocity and increasing the distance of the optical wave transmission.In addition,the coupling and evolution laws of the surface modes of metal-dielectric photonic crystals are studied to provide support for the study of slow optical waveguides.The main work is as follows:1.The magnetic photonic crystal unidirectional waveguide has the characteristics of unidirectional propagation and anti-interference,and can realize low-loss transmission.In this paper,through changing the structure of the unidirectional waveguide,surface defects are set on the surface of the magnetic photonic crystal unidirectional waveguide,and the dispersion of the unidirectional waveguide mode is modulated by the slow light mode formed by the surface defects.Studying the dispersion curve mode properties,it is found that the odd mode is more susceptible to boundary defect modulation than the even mode.It is this modulation that changes the shape and group velocity of the odd-mode dispersion curve.For this reason,we change the group velocity of the odd mode by changing the position of the dielectric columns on both sides of the unidirectional waveguide,and obtain a near-zero dispersion of one-way slow optical waveguide.2.Combining of the unidirectional boundary loop and the unidirectional air waveguide achieves optical delay by extending the transmission distance of the light wave in this paper.This is an innovation in this article.For unidirectional air waveguides,the odd and even modes appear at the same frequency range at the same time,and we independently stimulate a mode by changing the position of the source.The unidirectional mode has the characteristics of constructive interference,which makes the monochromatic electromagnetic wave transmit perfectly along the boundary of the rectangular circuit.Through the verification of time domain simulation,the optical delay effect is very remarkable.In particular,this composite waveguide realizes multiple functions of reducing scattering loss,optical delay,and unidirectional transmission.The optical delay time can be accurately adjusted by changing the length of the rectangular loop or increasing or decreasing the number of loops.3.A line defect waveguide is constructed on the basis of a two-dimensional metal-dielectric photonic crystal of a hexagonal honeycomb lattice,which can excite the dielectric waveguide mode and the plasma waveguide mode.The excitation and transformation of the two waveguide modes are controlled by adjusting the radius of the edge dielectric column,then observe and compare the group velocity,dispersion,and anti-jamming capabilities of two modes.We found that metal loss has no effect on the band structure through calculation.The plasma waveguide mode has stronger topological protection characteristics than the dielectric waveguide mode,and the group velocity is smaller,so that there are more advantages in the study of slow light,which can provide support for the design of the slow optical waveguide.