Research On Control And Application Of Surface Plasmons In Subwavelength Metallic Structures

The research work within this dissertation is supported by the National Key Basic Research Program of China(No.2006CB302905),the Key Program of National Natural Science Foundation of China(No.60736037),the National Natural Science Foundation of China(No.10474093)and so on.By using the two dimensional nonlinear finite difference time domain(FDTD)method,the roles of surface plasmons(SPs)and other optical modes in extraordinary optical transmission(EOT) are analyzed,beam deflection and focusing controlled by nonlinear optical effect are studied in micro-and nano-metallic structures containing nonlinear materials.Optical bistability is also numerically investigated in subwavelength metallic structures,and an ultrafast all-optical switching structure is designed and studied with a switching time of picosecond's level.The main research works and conclusions are as following:1.Based on two-dimensional FDTD method,the roles of SPs,Composite Diffracted Evanescent Wave(CDEW)and Cavity Mode(CM)are analyzed and distinguished in EOT of subwavelength metallic structures.The influences of structure parameters on these optical modes and far-field transmission are studied.By controlling the structure parameters,a single-pass transmission effect is achieved in subwavelength metallic structures with a maximal extinction ratio of 47.83dB.2.Based on nonlinear FDTD method,the influence of 3rd nonlinear effect is investigated on excitation,coupling,transmission and dispersive relation of SPs in micro-and nano-metallic structures containing nonlinear materials.The dynamic control of beam deflection,focusing and splitting is studied by modulating incident light.Large modulating ranges of deflection angle(8°～24°) and focusing distance(＞1μm)are achieved,which will offer great applications in near-field optics,SPs antenna and nano-integrate optics etc. 3.Optical bistability is numerically investigated in a subwavelength metallic grating coated by nonlinear material.The influences of structure parameters, such as thickness of nonlinear material and slit width of metallic grating,are studied on far-field transmission and bistability.The physical mechanism in the structure is analyzed by SPs and optical waveguide theory.Based on optical bistability,an ultrafast all-optical switching structure is designed with metal-dielectric composite nonlinear materials.The characters of far-field transmission,bistability and response time of the switching are studied and a shortest switching time of 0.2ps is achieved.Highlights of the dissertation are as following:1.The roles of SPs,CDEW and CM are analyzed and distinguished in EOT of subwavelength metallic structures.A single-pass transmission effect is achieved in subwavelength metallic structures with a maximal extinction ratio of 47.83dB.2.The dynamic controls of beam deflection,focusing and splitting is numerically studied for the first time in micro-and nano-metallic structures containing nonlinear materials.Large modulating ranges of deflection angle(8°～24°)and focusing distance(＞1μm)are achieved by nonlinear FDTD method.3.Optical bistability is numerically investigated in a subwavelength metallic grating coated by nonlinear material for the first time.An ultrafast all-optical switching structure based on bistability is designed with a shortest switching time of 0.2ps.