Propagation Properties Of Two-dimensional Photonic Crystal Waveguides Under Magneto-optical Effect

In recent years,the combination of magneto optical(MO)effect and photonic crystal(PC)has received more and more attention.In general,due to the band gap characteristics of the photonic crystal,the optical flow cannot be transmitted therein.In order to control the transmission of the optical flow in the photonic crystal,we can destroy the complete periodic structure of the crystal and construct some defects that results in the defect modes in the photonic band gap.If we introduce magneto-optical materials and apply external magnetic fields to it,there will be some interesting phenomenon.In this paper,we mainly study the coupling of magnetic surface defect modes.In the theoretical calculation,we have improved the traditional plane wave expansion method(PWM)and obtained the magnetic surface defect modes as well as the dispersion curve of the constructed model by which we obtain the transmission properties of the designed structure.The main works are as follows:1.Design a new optical waveguide switch.We divide the triangular lattice two-dimensional photonic crystal into two parts along the horizontal direction that leads to a photonic crystal waveguide.We use a layer of magnetic material yttrium iron garnet(YIG)to replace original rods in each side of the waveguide.When applied the external magnetic field in the same direction to several local YIG dielectric rods,there appears a local strong magnetic field in the center of the waveguide.Such a strong magnetic field could be regarded as a virtual “reflection wall” that prohibits the transmission of light flow.On the contrary,if the external magnetic field is removed,the “reflection wall” will disappear,and the optical flow transmission will be permitted in the waveguide.The function of the optical waveguide switch is realized.2.Basing on the previous research of optical waveguide switch,we will further study the special convex band when the saturated magnetic field is applied to all YIG dielectric rods.Because of the “negative refraction” effect of the convex band,the self-trapping of light and slow light can be achieved.When the optical frequency is in the self-trapping band,the light is localized near the point source that is due to the property of the mode itself instead of the effective reflection wall along the direction of the waveguide.When the light is in the slowlight band,the optical flow develops standing wave and moving standing wave at the center line and the boundary of the waveguide,respectively.3.In addition,we improved the original unidirectional waveguide and still using YIG as magnetic materials.We also design a model of cross-waveguide based on two-dimensional magneto-optic photonic crystal,which consists of horizontal and vertical unidirectional waveguides.For this model,we not only change the number of output ports,but also achieve the waveguide mode conversion,in which the even mode in horizontal waveguide is converted partly to the odd mode,which result in the hybridization of the two modes in vertical waveguides.