The Study Of Extraordinary Transmission Behavior In Sub-wavelength Metallic Slit

Ebbesen et al. firstly reported the phenomena of extraordinary transmission when light wave through arrays of sub-wavelength apertures on a piece of metallic film in 1998. After that, many scientists paid their attentions on this phenomena and the study on the transmission behavior of sub-wavelength metallic apertures has sparked a wealth of experimental and theoretical works in sub-wavelength optics. Slit is the most typical structure in various aperture structures, so the study on slit structure is very important. Besides, the extraordinary transmission phenomena makes sub-wavelength metallic slit have broad potential in developing optical equipments, detecting biologic molecules and so on. This paper is based on rigorous electromagnetic field theory, that is Maxwell's equations, and boundary integral method is adopted to analyze the extraordinary transmission behavior of various structure metallic slits. To our best knowledge, it is the first time that the investigation of horn-opened metallic slit has been reported. The main conclusions of this paper contain:[1] For the infinite structure sub-wavelength metallic slit, we have discussed its transmission behavior in various medium. The relationship between the wavelength of transmission peak and the refractive index of the surrounded medium is linear.[2] For the finite structure sub-wavelength rectangle metallic slit, we have studied the effects of different metal material and shapes of the slit on the transmission behavior. There are two transmission peaks on the transmission spectrum for the wavelength range: [500, 750]nm. We can draw a conclusion that the short-wavelength peak corresponds to the metal material and the long-wavelength peak corresponds to the geometry structure of the slit.[3] For the finite structure horn-opened metallic slit, we have discussed the transmission behavior for the cases of symmetric structure and asymmetric structure, respectively. Besides, we also find out the approximately equal optical properties between horn-opened slit and stepped slit.