Showing papers by "Zheyu Fang published in 2010"

Planar plasmonic focusing and optical transport using CdS nanoribbon.

Abstract: Planar plasmonic focusing of surface plasmon polaritons (SPPs) by an in-plane nanostructure consisting of Ag-column arrays and an in-plane Fresnel zone plate (FZP) with a Cu grating underneath for energy compensation was demonstrated. The CdS-based hybrid plasmonic waveguide generated in the Ag-column arrays was characterized with a scanning near-field optical microscope. By using the FZP focusing structure, the SPP modes were separated from the CdS photoluminescence background and focused at the FZP focus area, and in this way, were used as the source for the SPP waveguide. Finite-difference time-domain simulations correspond with the experimental observations, suggesting that this is indeed an effective approach to control SPP coupling within the dielectric nanoribbon waveguide.

Surface Plasmon Polariton Enhancement in Silver Nanowire–Nanoantenna Structure

Abstract: The surface plasmon polariton (SPP) coupling and enhancement in silver nanowire–nanoantenna structure is proposed and simulated by using finite difference time domain method. The results demonstrate that three-arm antenna can effectively enhance the coupling efficiency at the incident end and the SPP field intensity at the emission end. The enhancement factor, which is defined as the ratio of the SPP field intensity at the emission end with and without the three-arm antenna, for the various antenna arm lengths and incident wavelengths under different incident angles are calculated. The suggested structure can be served as an enhanced plasmonic waveguide for the nanophotonic and plasmonic circuits in the future.

Hybrid Plasmonic Waveguide Based on Tapered Dielectric Nanoribbon: Excitation and Focusing

Abstract: The nanofocusing of light source was proposed and simulated using the dielectric-loaded surface plasmon polariton (SPP) model with various laterally tapered planar dielectric architectures on the top surface of the metal. By using finite-difference time-domain method, enhancement factor for the local electric field under distinctive incident polarization was analyzed with different taper apexes under various incident wavelengths and incident angles of the excitation laser. The SPP dispersion and the effect of dissipation on adiabatic nanofocusing of SPP in a sharp taper structure were used to predict the optimal taper angles of the structure and to explain the phenomena of SPP wave slowing down as it propagating toward the taper end. This SPP nanofocusing process was also experimentally realized by illuminating the structure of a tapered CdS nanoribbon deposited on the Ag surface. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits.

Near-field nanofocusing through a combination of plasmonic Bragg reflector and converging lens

Abstract: We report the near-field nanofocusing through a plasmonic lens containing a Bragg reflector and a converging lens, which consist of semitransparent annular grooves milled into a gold film with different periods along the radial direction. By illuminating the structure with a linearly polarized light, two tightly focal spots were detected by scanning near-field optical microscope. This plasmonic lens has considerably reduced direct light transmission, making the focal spots obvious. By raising the radius of half of every groove, one single spot was obtained. Furthermore, theoretical simulations prove that the light intensity of the focal spots can be doubled through adding the Bragg reflector surrounding the converging lens.

Color-changeable properties of plasmonic waveguides based on Se-doped CdS nanoribbons

Abstract: The color-changeable optical property induced by the resonance of surface-plasmon polaritons (SPPs) based on a ternary alloy ${\text{CdS}}_{0.65}{\text{Se}}_{0.35}$ (CdSSe) nanoribbon partly placed on an Ag film was reported. The spectroscopic redshift of in situ CdSSe photoluminescence under different incident laser powers was characterized by using scanning near-field optical microscopy. The propagation length, mode area, and confinement factor of the SPPs were also investigated. The trade-off between the spectroscopic shift and plasmonic resonance was demonstrated with the Franz-Keldysh effect and simulated by using the finite-difference time-domain method. The suggested plasmonic structure provides valuable information for the implementation of photonic integrated nanocircuits, especially for the color-changeable plasmonic device.

Antenna-mediated coupling of light into Ag nanowire.

Abstract: The antenna-mediated coupling of light into Ag nanowire is investigated both in experiments and simulations. The coupling efficiency is strongly depended on the architecture of the metallic particles related to the Ag nanowire. Different incident angles of excitation laser are also tested for the maximum coupling effiecieny. The results demonstrate three-arm triangle antenna group fabricated at the incident end can effectively enhance the surface plasmon polariton (SPP) coupling and propagation. The SPP resonance and the Fabry-Perot cavity theory are used to explain the plasmon enhancement and propagation phenomena. The suggested structure can be served as an enhanced plasmonic waveguide for the nanophotonic and plasmonic circuits in the future.

PLASMONIC FOCUSING BASED ON CdS NANORIBBON

Abstract: In this paper, we propose and simulate the surface plasmon polariton nanofocusing process by using Finite-difference Time-domain (FDTD) method. The maximum enhancement factor at the taper end area is optimized with different wavelength of the excitation laser. With the advantage of SNOM, the SPP nanofocusing is experimentally observed by illuminating the tapered CdS nanoribbon deposited on the Ag film. The SPP dispersion is used to predict the optimal taper angles of the structure. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits.