Xuan Tang

Vertical coupling between short range surface plasmon polariton mode and dielectric waveguide mode

Coupling performance between a short range surface plasmon polariton (SRSPP) mode and a conventional dielectric waveguide mode is demonstrated numerically. Simulation results show that the coupling length, as short as tens of microns, can be realized because the field of SRSPP extremely concentrates to the metal surface. SRSPP-based hybrid coupler provides not only an approach to realize highly compact functional devices, such as the TE-pass polarizer with high performance, but also an integratable route for efficiently exciting SRSPP mode, which is very useful in the SRSPP-based biosensor or SRSPP-assisted emission enhancement devices.

Temperature dependence of ministop band in double-slots photonic crystal waveguides

We proposed and fabricated a double-slots photonic crystal waveguides (PCWGs) structure formed by introducing two slots into PCWGs with air-bridge structure on silicon-on-insulator substrate. The mode characteristics of double-slots PCWGs were investigated theoretically and experimentally. The transmission spectra present a sharp and deep dip (22 dB with bandwidth of 6 nm) caused by ministop band in the proposed structure, which is 15 dB deeper than that in the W3 PCWG. Additionally, dependence of the dip on temperature in the double-slots PCWG was measured and a temperature coefficient 0.159 nm/°C can be concluded.

Hybrid three-arm coupler with long range surface plasmon polariton and dielectric waveguides

The characteristics of the asymmetric hybrid three-arm coupler, which consists of one middle long range surface plasmon polariton waveguide and two outside conventional dielectric waveguides, are analyzed numerically with finite element method.

Tunable surface plasmons for emission enhancement of silicon nanocrystals using Ag-poor cermet layer

To improve the quantum efficiency from silicon nanocrystals, a structure with Ag∕Ag-poor cermet layers is proposed. Due to large permittivity of Ag-poor cermet and its dispersion characteristic, density of states can be enhanced at the energy much lower than the plasmon energy of Ag. By properly choosing the component of the Ag-poor cermet, the dispersion of surface plasmons can be engineered to increase radiative emission rate significantly at the emission energy of silicon nanocrystals. Effective enhancement is theoretically demonstrated using Ag, which was generally recognized as nonideal material for emission enhancement in silicon nanocrystals due to its high plasmon energy.

Numerical solution of surface plasmon polariton mode propagating on spatially periodic metal-dielectric interface

To obtain the numerical solution of normal surface plasmon polariton (SPP) modes of free oscillations of the electromagnetic field on a cylindrical periodic dielectric-metal interface, a combination method is proposed by taking advantage of Greens function method and Chandezons approach. With such methods, the dispersion curves and electromagnetic field distributions of SPP modes are calculated based on an Au-Si3N4 interface with both sinusoidal and symmetrical sawtooth shapes. The simulation results prove that the proposed method can be applied for calculating the electromagnetic field distribution of the SPP mode at an arbitrary wave vector along the dispersion curve and on arbitrary interface shapes. Furthermore, good stability and sufficient accuracy can be obtained with moderate frequency searching steps and a coefficients matrix order.

Photoluminescence with ultra-wide spectrum from radiative defects in Si-rich SiN x

The photoluminescence spectra of amorphous silicon rich silicon nitride films with various compositions were investigated. Two main luminescence peaks were identified for all samples and blueshift of photoluminescence were observed after annealing treatment. With the help of X-ray photoelectron spectroscopy and Fourier transform infrared measurement, the chemical composition and bonding environment of samples, which were grown with different reactant gases flow rates of plasma enhanced chemical vapor deposition, were analyzed. According to all these measurement results, it is confirmed that the main luminescence centers are radiative recombination defects, such as silicon and nitride dangling bonds. With proper deposition conditions, all these radiative recombination defects could be activated at the same time, so that ultra-wide photoluminescence spectra with full width at half maximum of about 250nm ∼ 300nm were obtained in visible region.

Passive and active performances of slab photonic crystal waveguides

Two dimensional slab photonic crystal waveguides were designed and fabricated. Full photonic band gap, band gap guided mode, and mini-stop-bands were observed. Passive and active performances were investigated theoretically and experimentally.

Electroluminescence Enhancement from Silicon Nanocrystals Using Doublelayer Surface-Plasmon Waveguide

Using doublelayer surface-plasmon waveguides, Purcell factor can be improved dramatically. Current-voltage characteristics have been investigated for low voltage electroluminescence operation.

Surface-Plasmon-Enhanced photoluminescence from Nano-Porous Silicon Layer

In this paper, we report experimental results to demonstrate the enhancement of the photoluminescence from nanostructural porous silicon due to Purcell effect of the metal surface plasmons.

Internal Quantum Efficiency Enhancement of Silicon Nanocrystals Using Doublelayer Au Film Surface-Plasmon Waveguide

Using double layer Au film surface-plasmon waveguides, Purcell factor can be improved dramatically. Under the same background loss, more significant enhancement in internal quantum efficiency of silicon nanocrystals can be obtained compared with the monolayer structure.