The Study On Optical Switches And Filtering Characteristics In Waveguide-Resonator Coupled System

Obtaining high sensitivity, low threshold all optical switch and optical modulator is the foundation of integrated nanophotonics. Waveguide resonant cavity hybrid structure combine the properties of waveguide and resonant cavity’s characteristics. It provides an opportunity to realize integrated nanophotonics. Waveguide resonant cavity hybrid structure has significant application in optical buffer, optical modulate, all optical switch, optical filter and Dense Wavelength Division Multiplexing system. This thesis mainly study the optical properties of optical structure and the optical characteristics of all optical switch. Using two dimensional FDTD simulation method, some photonic devices are proposed.First, we study the optical characteristics of straight waveguide resonant cavity hybrid structure. The results show that stopband appears in the transmission spectra. And the stopband shows sensitive to the refractive index changes of the filled media inside the ring cavity. In addition, the simulation results reveal that the dual-ring cavity waveguide configuration with Kerr nonlinear material can act as a double channel all-optical switch. The contrast ratios of the two switch channels is 16.6 dB and 10.37 dB, respectively. Subsequently we also designed a bidirectional all-optical switch based on two parallel waveguides coupled to ring cavity structure. Lastly, multi-channel optical switches are achieved by increasing the number of cavity.Next, we study an optical switch with graphene material based on the metal-insulator-metal waveguide. And the transmission characteristics of this optical switch were numerically studied. The proposed optical switch is composed of an input MIM waveguide, two output MIM waveguides and two graphene sheets. The results show the dual states of the graphene material. By utilizing the gate-voltage-dependent optical properties of graphene, these hybrid structures exhibit outstanding optical switch characteristics. To further study a graphene resonator plasmonic switch, we introduce a ring graphene resonator, which can be designed by applying different bias voltages to different locations to create nonuniform dielectric constant, the switch has the advantages of small size and easy tuning. These results would be helpful for designing hybrid optical switch with specific usage.Subsequently, we proposed and studied a new tunable plasmonic filter at near infrared band. The proposed integrated plasmonic filter combines liquid crystal (LC) material with an optofluidic control system. The simulation results show that the resonant wavelength can be controlled by increasing the length of the LC column length and swithcing the LC between ordinary state and extraordinary state. In addition, We proposed a tunable power splitter based on metal-dielectric metal (MDM) waveguide coupled with rectangle cavity with Kerr nonlinear material. Using couple mode theory and two dimensional FDTD simulation method, transmission characteristic is calculated, results show that the output power ratio can be efficiency tuned by varying the control light intensity.Lastly, we study the plasmon coherent phenomenon based on a rectangle resonator side coupled with a MIM waveguide. First, we observe plasmon induced transparency in rectangle resonators side coupled with a MIM waveguide, by changing the geometric parameters of the rectangle resonator, we can tune the location and bandwidth of the window. Then, double plasmon induced transparency response is observed when two nanobars are located in proximity to the silver nanodisk. The PIT window wavelength and bandwidths can be efficiently tuned by controlling the geometric parameters (such as the lengths of nanobars and the coupling distances between the nanodisk and nanobars. Lastly, a MIM waveguide-slot resonator system with a metal nanowall was proposed and investigated both by theoretical and FDTD simulation, we found the complex coupled system exhibits a Fano resonance, induced by the interaction between the modes supported by the rectangle resonator and the nanowall. The sharp asymmetric Fano line shape can be controlled by changing the thickness of the nanowall or the distance between the reference plane and the metal nanowall. The studies in this paper play a guiding role for the the designing and manufacturing of photon devices.