Study On Optical Logic Gate Based On Surface Plasmon Polaritons

Surface Plasmon Polaritons(SPPs)is a kind of electromagnetic wave which formed by the interaction between the external photon and the free electron in the metal.It is limited to propagate along the direction of the metal-medium.SPPs has an unique optical property that can break through the traditional diffraction limits,The size of optical devices based on SPPs waveguides can be controlled within the subwavelength scale,so it plays an increasingly important role in the miniaturization and high integration of optical communication devices.In this thesis,we mainly study all-optical logic gates based on surface plasmon polaritons.Follows are the main contents and the highlights:1.An optical switch and an AND logic gate based on the Spin-Orbit Interaction of Light are proposed in this thesis.We can get a conclusion that Localized Surface Plasmon on the tip of the metal nanowire coupling with the orientated propagating Surface Plasmon Polaritons,which leads to the spin-propagating Surface Plasmon Polaritons.Therefore,we design a Y-shaped metal structure,which can produce SPPs which propagating along the surface of the Y-shaped structure by coupling with a circularly polarized light.We control the propagated direction of SPPs to control the surface plasmon to shoot out from different guide.We calculate the transmission of light and choose a suitable threshold to realize the optical switch,and place a tooth shaped structure on one of the guide of the Y-shaped structure to adjust the extinction ratio of the light switch.After that,we cascaded two Y-shaped structure,and choose appropriate threshold to realize AND logic gate.In this thesis,using the different polarization states of circularly polarized light to realize the basic logic coding.LCP is defined as logic 1 and RCP as logic 0.2.In this thesis,a kind of NAND logic gate and NOR logic gate based on the coupling theory of metal nanowaveguides and circular resonators are proposed.A circular resonator system coupled with MIM waveguide is designed.When the waveguide is coupled with the circular resonator,if the frequency of the incident light and the frequency of the circular resonator are the same,the resonant mode in the circular resonator will be excited,and the incident light will be transferred from one waveguide to another.When the incident light frequency is far away from the resonant frequency,almost all the incident light will be reflected back.We analysed the transmission of the incident light through the structure,the basic NAND logic gate can be realized by controlling the state of the input port.After that,the basic NOR logic gate is realized by adjusting the position of input port and output port.The influence of the radius of the circular cavity,the coupling distance between the rectangular waveguide and the circular cavity on the simulation performance and the length of the rectangular waveguide is also be analyzed.