Research On The Propagation Characteristics Of Two-dimensional Photonic Crystal Waveguide

With the application and development of optical technology in the field of communication and information,high-speed optical integrated circuit technology has also become the frontier of research in the field of communication and information,and the construction and design of optical circuit components have subsequently become one of the focuses of scientific research.The optical circuit element is generally formed by a combination of optical waveguides such as photonic crystals having a discontinuous or non-uniform medium in the propagation direction of light.The rise of photonic crystals has made it possible for people to manipulate photons.At the same time,with the rapid development of nanotechnology,surface plasmon has also shown its advantages in the field of nano-optics.Photonic crystals made of dielectric and metallic silver have unique optical properties and have unique application value in optical communication,optical sensing,and antennas.In this paper,the Fourier series expansion method is used to analyze photonic crystals with infinitely long chain structure with different dielectric constants,different sizes and different shapes.First,we deeply studied the propagation distribution,electric field distribution characteristics and convergence of the single-layer periodic infinitely long square chain structure with and without PML.In terms of physical properties,the three propagation modes of the square chain structure in three Bragg propagation periods are studied in detail,including propagation mode,leakage mode,and cut-off mode.Each mode has different manifestations in the three propagation cycles.At the same time,a variety of complex characteristics are also considered,for example,the direction of the wave and the propagation path of the energy have two forms:co-directional and reverse(that is,unidirectional and bidirectional);the various distribution states of leakage waves,such as attenuation and divergence.By analyzing these new physical characteristics,it lays a solid foundation for in-depth development and application of leaky antennas and other applications.Secondly,taking the periodic structure of a single-layer dielectric cylinder as the research object,the numerical characteristics are analyzed in detail.At the same time,in order to make the method used in this paper more convincing when studying the structure,under the same structure and parameters,another method grid and technology-Lattice Sums technique(LST)is used to obtain the complex propagation constant and the Fourier series with PML used in this paper.Expansion method for comparison.Next,the complex propagation constant of the infinitely long silver nanorod array plasma structure in the range of 180nm-1900 nm was calculated by Fourier series expansion method(FSEM),and the characteristics of the complex propagation constant were analyzed in depth.At the same time,the propagation constants calculated from the following four sets of experimental data are in good agreement:(1)Fourier series expansion method uses Johnson dielectric constant experimental data(2)Generalized multipole technique(GMT)uses Johnson dielectric constant experimental data(3)Fourier series expansion method uses Palik dielectric constant experimental data(4)FSEM uses the dielectric function obtained by the Drude-Lorentz model.Confirmed the method used in this paper to study the accuracy and reliability of the structure.In addition,a finite array of only 40 silver nanorods was studied,and the wave-guiding capability of the finite array under the excitation of a plane wave of a specific wavelength was discussed.According to their different conduction capabilities(propagation,attenuation,cut-off),they can be used in waveguides,sensors,filters and other devices.Finally,the numerical characteristics and field pattern distribution characteristics of the cylindrical periodic structure of two-layer,four-layer,and eight-layer media are studied.The multi-layer structure has the phenomenon that both odd and even modes exist simultaneously,and the periodic structure of the four-layer and eight-layer dielectric cylinders has a phenomenon corresponding to multiple odd-mode frequencies.This structure can be applied to transmission devices such as multi-mode communication.