Showing papers by "Zheyu Fang published in 2009"

Focusing surface plasmon polariton trapping of colloidal particles

Abstract: We report focusing surface plasmon polariton (SPP) trapping of colloidal particles without optical interactions. Using a silver nanostructure, we demonstrate SPP launching and propagation under a p-polarized incident laser. In-plane Fresnel zone plate (FZP) is used to focus the SPP waves. Colloidal particles can be trapped at the silver nanostructure in the illumination region and the FZP focus area by focusing SPP force. The SPP tweezers open new perspectives in the subwavelength trapping and applications to lab-on-chip devices.

Color-tuning and switching optical transport through CdS hybrid plasmonic waveguide.

Abstract: We report the color-tuning and switching optical transport characters of CdS hybrid plasmonic waveguide by using near-field optical microscopy. The guided photoluminescence spectra under various waveguide lengths demonstrate a spectroscopic red-shift for the part of CdS nanoribbon placed on the sapphire substrate and an energy compensation at Ag film. Surface plasmon polariton leakage and radiation are explored by near-field characterizations. Finite difference time domain simulations have good agreement with the experimental observations of subwavelength confinement and propagation. With a strong end facet emission, the suggested hybrid plasmonic waveguide can serve as a color-changeable optical nanosource in integrated photonic devices.

Surface plasmon-enhanced micro-cylinder mode in photonic quasi-crystal.

Abstract: Two-dimensional micro-cylinder patterns of dodecagonal photonic quasi-crystal (12-PQC) and tetragonal photonic crystal (2-PC) were fabricated on the top surface of a GaN light-emitting diode (LED). The patterns were evaporated with a 10-nm-thick Ag film. Spatially resolved surface emission was recorded and analysed by scanning near-field optical microscopy. Electromagnetic energy was confined and enhanced at the top surface when the surface plasmon (SP) resonated. The enhancement factor for 12-PQC was 1.9 times that of 2-PC, 8.6 times that of non-patterned LED in the near field and 6.7 times in the far field, respectively. Finite-difference time-domain simulations are consistent with the experimental data. The results show that with a patterned structure on the top surface of an LED, the light emission can be greatly enhanced due to SP resonance.

DFT Study of Structural and Thermodynamic Properties for Polybrominated 5,10-Dihydrophenazines

Abstract: The structural and thermodynamic properties of 75 polybrominated 5,10-dihydrophenazines (PBDPs) in the ideal gas state at 298.15K and 1.013 × 105 Pa have been calculated at the B3LYP/6-31G* level using the Gaussian 03 program. The isodesmic reactions are developed to calculate the standard enthalpy of formation (ΔfHθ) and standard free energy of formation (ΔfGθ) of PBDP congeners. The relationships of these thermodynamic parameters with the number and position of the Br atom substitution (NPBS) are discussed, and it is found that there exists a high correlation between thermodynamic parameters and NPBS. In addition, the correlations between structural parameters and NPBS are discussed. High correlations were found between the energy of the highest occupied molecular orbital (EHOMO), the most negative atomic partial charge in the molecule (q−) and NPBS, and all R2 values are larger than 0.90.

Optical waveguide behavior of Se-doped and undoped CdS one-dimensional nanostructures using near-field optical microscopy

Abstract: The optical waveguide behaviors of CdS and CdSxSe1−x nanostructures are studied using near-field optical microscopy. Optical measurements demonstrate that light may be guided on sub-wavelength scales along CdS nanoribbons in straight or bent structures. The photoluminescence (PL) spectra from nanoribbon emission using scanning near-field optical microscopy are analyzed under different incident laser intensities. The PL spectra along Se-doped and undoped CdS nanoribbons at different propagation distances are investigated. Both the guided PL spectra of Se-doped and undoped CdS nanoribbons show red-shifts because of the band-edge absorption. Our results are useful for the development of new kinds of functional nano devices.