Cui Yiping

Bound modes analysis of symmetric dielectric loaded surface plasmon-polariton waveguides.

A symmetric dielectric loaded surface plasmon polariton waveguide is proposed and numerically analyzed. The characteristics of the symmetric and asymmetric bound modes, including the effective mode indices, propagation lengths, mode sizes and mode shapes at telecom wavelength 1.55 microm are investigated in detail. The simulation results show that the sub-wavelength confinement (about1.45 microm ) and a long propagation (about 820 microm ) can be realized. Although the mode sizes are a bit larger than that of the dielectric loaded surface plasmon polariton waveguide, an order longer propagation length can be achieved. The proposed symmetric dielectric loaded surface plasmon polariton waveguide provides a potential for low loss and high density photonic integration.

Fano Resonances Induced by Strong Interactions Between Dipole and Multipole Plasmons in T-Shaped Nanorod Dimer

A simple T-shaped plasmonic nanostructure composed of two perpendicular coupled nanorods is proposed to produce strong Fano resonances. By the near-field coupling between the “bright” dipole and “dark” quadrupole plasmons of the nanorods, a deep Fano dip is formed in the extinction spectrum, which can be well fitted by the Fano interference model. The effects of the geometry parameters including nanorod length, coupling gap size, and coupling location to the Fano resonances are analyzed in detail, and a very high refractive index sensitivity is achieved by the Fano resonance. Also by adjusting the incident polarization direction, double Fano resonances can be formed by the interferences of the dipole, quadrupole, and hexapole plasmons. The proposed nanorod dimer structure is agile, and a trimer which supports double Fano resonances can be easily formed by introducing a third perpendicular coupled nanorod. The proposed T-shaped nanorod dimer structure may have applications in the fields of biological sensing and plasmon-induced transparency.

Design of a compact and high sensitive refractive index sensor base on metal-insulator-metal plasmonic Bragg grating.

A nanometric and high sensitive refractive index sensor based on the metal-insulator-metal plasmonic Bragg grating is proposed. The wavelength encoded sensing characteristics of the refractive index sensor were investigated by analyzing its transmission spectrum. The numerical results show that a good linear relationship between the Bragg wavelength and the refractive index of the sensing material can be obtained, which is in accordance with the analytical results very well. A high refractive index sensitivity of 1,488 nm/RIU around Bragg resonance wavelength of 1,550 nm was obtained. Besides, the simulation results show that the sensitivity is depended on the Bragg resonance wavelength and the longer the Bragg resonance wavelength, the higher sensitivity can be obtained. Furthermore, the figure of merit of the refractive index sensor can be greatly increased by introducing a nano-cavity in the proposed plasmonic Bragg grating structure. This work pave the way for high sensitive nanometric refractive index sensor design and application.

Characteristics analysis of a hybrid surface plasmonic waveguide with nanometric confinement and high optical intensity

A hybrid surface plasmonic waveguide with nanometric confinement is proposed. With interactions between high-index-contrast dielectric waveguide modes and surface plasmon modes of a very thin metal film, nanometric hybrid surface plasmon modes with high optical intensities can be formed. Characteristics of the symmetric and asymmetric hybrid surface plasmon modes, including the effective mode indices, propagation lengths, mode sizes, and power intensities at telecom wavelength (1550 nm), are investigated in detail. Simulation results show that nanometric mode confinement and a long propagation length can be realized simultaneously. The high optical power intensity and long propagation length of the nanometric hybrid surface plasmon modes are very promising for high-density photonic integration and nonlinear waveguide applications.

Tris (8-Hydroxyquinoline) Aluminium Nanostructure Film and Its Fluorescence Properties

Tris (8-hydroxyquinoline) aluminium (Alq3) nano-structured films are fabricated by the gas evaporation method, and their fluorescent properties are investigated in detail. Compared with the conventional amorphous Alq3 films, the fluorescent efficiency of the nanostructure films is enhanced to a certain extent.

Fano resonances in a plasmonic waveguide system composed of stub coupled with a square cavity resonator

A coupled plasmonic waveguide resonator system which can produce sharp and asymmetric Fano resonances was proposed and analyzed. Two Fano resonances are induced by the interactions between the narrow discrete whispering gallery modes in a plasmonic square cavity resonator and the broad spectrum of the metal–insulator–metal stub resonator. The relative peak amplitudes between the 1st and 2nd order Fano resonances can be adjusted by changing the structure parameters, such as the square cavity size, the stub size and the center-to-center distance between the square cavity and the stub resonators. And the 1st order Fano resonant peak, which is a standing-wave mode, will split into two resonant peaks (one standing-wave mode and one traveling-wave mode) when it couples with the 2nd Fano resonance. Also, the potential of the proposed Fano system as an integrated slow-light device and refractive index sensor was investigated. The results show that a maximum group index of about 100 can be realized, and a linear refractive index sensitivity of 938 nm/RIU with a figure of merit of about 1.35 × 104 can be obtained.

Degeneracy and Split of Defect States in Photonic Crystals

One-dimensional photonic crystals with two or more structural defects are studied. We observed an interesting characteristic of transmission band structure of photonic crystals with defects using the transmission-matrix-method simulation. The transmission states in the wide photonic band gap caused by defects reveal degeneracy and split in certain conditions. Every split state is contributed by coupling of all defects in a photonic crystal. Using the tight-binding method, we obtain an approximate analytic expression for the split frequency of photonic crystals with two structural defects.

Negative Refraction of a Symmetrical π-shaped Metamaterial

A symmetrical π-shaped metamaterial is investigated. Numerical simulations exhibit the negative-refractive property of this structure. The complex refractive index n, wave impedance z, effective permittivity and effective permeability μ have been retrieved from the simulated S parameters. The negative-refractive band lies between 11.2GHz and 13.05GHz. The frequency band with high transmission with low loss occurs between 11.95GHz and 12.5 GHz, which is helpful for practical applications. The mechanism of the electromagnetic resonance is also revealed.

Evolution of Luminescence with Shell's Thickness in Colloidal CdSe/CdS

We synthesize colloidal CdSe/CdS core/shell quantum dots with different shell thicknesses, and there are five samples including CdSe core dots, and CdSe/CdS core/shell dots with 1–4 CdS layers. X-ray diffraction and Raman measurements indicate that the stress in CdSe core becomes stronger with the increasing shell thickness, and the optical measurements show that when the shell becomes thicker, the photoluminescence quantum yield is enhanced, and the radiative decay is also expedited. The temperature-dependent optical spectra are measured. The relation between the microstructure and the optical properties is discussed.

Polymer waveguide Bragg grating Fabry–Perot filter using a nanoimprinting technique

A narrow band waveguide Fabry?Perot filter at 1550 nm, which is composed of two polymer waveguide Bragg gratings as reflectors, is presented. By using conventional lithography, a low-loss polymer channel waveguide was fabricated, and the submicron Bragg grating structure was transferred onto the waveguide surface using a nanoimprinting technique. The transmission spectrum of the device was measured, and the results show that there is a very narrow transmission peak, with a 3 dB bandwidth of 0.011 nm in the 0.38 nm rejection band of the waveguide Bragg grating. A quality factor of Q???1.41???105 is achieved. The insertion loss and the extinction ratio of the Fabry?Perot filter are about ?12.5 dB and 17 dB, respectively. In addition, the measured transmission spectrum is in excellent accordance with the numerical simulation.