Design And Transmission Characteristics Investigation Of Photonic Devices Based On Defect Photonic Crystal

The emergency of new material explored by Human beings will generally lead to novel technologies in engineering. In1987, in the studies of the radiation properties and photon localization of material with refractive index changes, Yablonovitch and John independently put forward a new concept of "photonic crystal". They found that the propagation characteristics of light through photonic crystals are different from ordinary materials, which makes it possible for people to manipulate and control the photons. Though there has been much studying on perfect photonic crystal structures, the unique characteristics of defect structure photonic ctystals cause more attention of researchers. This is because photonic crystal point defects and line defects have many practical applications, such as photonic crystal lasers, photonic crystal waveguides, photonic crystal filters.In this paper, we studied the photonic band gap, transmission characteristics, light transmission properties of photonic crystal by using the plane wave expansion method, the finite difference time domain method and transfer matrix method. We optimally designed the photonic crystal micro-nano photonic devices, explored the application of defect photonic crystal in dispersive separator, all-optical diode, photonic crystal waveguide, power splitter, light-emitting diodes and other fields, some important results are obtained. The main research conclusions are:1. A new type of one-dimensional photonic crystal dispersion separator was designed. The device used twin prisms as a center defect. Different from a general photonic crystal defect mode which is dependent on the defect properties including thickness and refraction index, the wavelength of defect mode of current structure is dependent on the incident position on the first interface of the structure for a fixed defect. That is, at different incidence points, the structure has different transmitted wavelengths. We further studied the transmission properties of the structure with different thicknesses and refractive indexes of the twin prisms. The wavelength of defect modes varies from O.9λ0to1.02λ0with a linear relationship between the location,These characteristics can be used as a new type of dispersion separator. The bandwidth of dispersion separator has218um and the resolution can be up to0.0127λ0(where λ0is the the intrinsic wavelength of photonic crystal). 2. Basing on the effect of photon tunneling, we studied the transmission properties of a non-symmetrical nonliear cavity. The non-symmetrical nonliear cavity structure is formed by a nonliear cavity with two all reflective coupling prisms. The two air layers between the prism and the cavity have different thicknesses. It is found that a unidirectional diode-like transmission occurs with this structure. For the same incident frequency and incident intensity, light is at switch-on status for left incidence, while the light is at switch-off status for right incidence. The structure can be used to achieve all-optical diode.3. A novel photonic crystal1x2splitter is designed based on the self-imaging of multimode interferences in the two-dimensional square photonic crystal waveguides. The positions of output waveguides are determined by the positions of two-fold image which is formed by the self-imaging effect of multimode interferences. The reflective losses are obviously decreased by inserting two dielectric rods at the junctions between the multimode waveguide and single-mode waveguide. The interted rods can change the mode field of the coupling zone due to the mode field match. The results show that the transmittance of this splitter can reach93%for λ=1.55μm.4. The coupling of three parallel photonic crystal waveguides can be considered as a multimode interference system in the two-dimensional square photonic crystal. the positions of output waveguides is decided by the positions of periodic twofold image which are formed by the self-imaging effect of multimode interference. The reflective losses are obviously decreased by shifting a dielectric rod in the junction between the multimode waveguide and single-mode output waveguide, which will form a microcavity, it can vary and match the mode field of the coupling zone. The1x2splitters of photonic crystal directional coupling waveguide is designed with a micro cavity structure, not only the transmittance of this splitter can be as high as99.04%for λ=1.55p.m but also it can work in wide spectral range from1.50μm to1.60μm with very high transmissivity.5. The design of a novel photonic crystal waveguide large separating angle1x3power splitter is presented. The proposed power splitter has three output ports, the coupling among three parallel photonic crystal waveguides can be considered as a multimode interference (MMI). The output optical power in each port can be controlled by adjusting the radii or refractive index of the dielectric rods in the coupling region.It is due to the changes of the phase distribution of the electromagnetic fields in the coupling region.The results indicate that1x1,1x2and1x3type power splitters can be realized when the normalized radius of dielectric rods in the coupling region are0.130,0.180,0.152or0.221, respectively.6. The light extraction efficiency of triangular lattice photonic crystal light emitting-diode(LED) are studied by using the three-dimensional finite-difference time-domain(FDTD) method based on dipole source model. The effect of polarization angle on the light extraction efficiency of LED for magnetic dipole is smaller than that for the electric dipole. Thus the model of magnetic dipole is more close to real case. We optimally designed a kind of triangle lattice with air holes LED structure. We used a magnetic dipole source model. The enhance factor of the light extraction efficiency can be up to4.5. At the same time, the far field characteristics were studied by near field to far field transformation method. The results show that the far-field divergence angle of photonic crystal LED is small which lead to a good directivity.