| The coupling between free electrons oscillation in the metal surface and the incident light leads to electromagnetic modes that are tightly confined to the metal surface, including propagated surface plasmon polariton (SPP) and localized surface plasmon(LSP). Their excellent features with ultra-fast response speed, subwavelength localizing and field enhancement make them of great importance in all-optical circuit, data storage, communication, imaging, bio-sensing, solar cell and other applications. With the continuous improvement of micro-fabrication technology in recent years, through the metal surface structure designing SPP and LSP can be controlled effectively, which greatly enhances people’s ability to manipulate light. Thus, the "plasmonics" has become one of the most popular research fields.The work in this paper is just based on the background of plasmonics. By micro-structure designing on the metal surface, we experimentally and theoretically investigated the regulation of EM field distribution, polarization dependence and optical responses of artificial structures. The main contents include spatial non-diffraction beams based on SPP, polarization dependent beams based on dielectric loaded surface plasmon polariton waveguide (DLSPPW) and the optical properties of complex planar metamaterial.1) Because of diffraction effects, the width of optical beams will broaden and the energy will decay rapidly in the process of propagation. However, the non-diffracted beams can transcend the limitation of diffraction effects and they are very promising in optical information transfer, integrated photonic devices and particle manipulation applications. We derived the mathematical form of Bessel beam, Airy beam and nonparaxial Bessel beam and Mathieu beam from the Helmholtz equation. A phase modulation method was proposed based on SPP. In this method, we converted propagating SPP to spatial Airy beam and Bessel beam by non-periodic metal grooves successfully. And the properties including non-diffracting, self-bending and self-healing are well demonstrated by experiments and simulations.2) The phase modulation method can be easily used to implement other forms of spatial field distribution such as focusing, line focusing and collimation. Focusing is one of the basic operations in light manipulations. It is the key point in light concentration, light detection, imaging and other applications. Through a simple transformation of the phase modulation method, oblique focusing can be realized. Furthermore, we realize mode dependent oblique focusing in DLSPPW system. Experimentally the focusing of orthogonal waveguide modes TMo and TEo was realized at different positions, which can be dynamically controlled by the polarization of incident light.3) Periodic structures have been widely investigated to achieve desired far-field frequency response and near-field distribution. For the convenience in fabrication, planer metamaterials have been widely and deeply studied. We have designed a composite metamaterial with a continuous morphology, each of its repeating units composed of two hetero-connected SRR chains. This structure can support two dark modes in the near infrared region, which are symmetric and antisymmetric hybridization modes, respectively. We studied the origins of these two modes and their excitation conditions by simulation and the theory of modes hybridization. And the hybridization modes of the double-chain array and single "metamolecule" were both calculated and compared. Our results may be useful for the investigation and design of complex metamaterials and their applications in dynamic regulations. |
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