Review of numerical and approximate methods for the modal analysis of general optical dielectric waveguides

AbstactAbstact This paper reviews numerical and approximate methods for the modal analysis of general optical dielectric waveguides with emphasis on recent developments. Six groups of methods are reviewed, covering (1) the finite-element method, (2) the finite-difference method, (3) the integral-equation method, (4) methods based on series expansion, (5) approximate methods based on separation of variables, and (6) methods that do not fit into the above groups, ranging from the specialized ones for analysing restricted classes of waveguides to the most general ones for analysing inhomogeneous, arbitrarily-shaped, anisotropic waveguides. Some suggestions with regard to the selection of methods for particular applications are given.     

Design of an acoustic bending waveguide with acoustic metamaterials via transformation acoustics

Transformation acoustics is employed to design an acoustic bending waveguide. A two-dimensional square area with anisotropic and homogeneous material properties is transformed into a fan-shaped area with anisotropic and inhomogeneous material properties to rotate the direction of beam propagation. An alternating layered structure is considered to approximate a medium with anisotropic material properties. From the calculation results, the transformation medium can be realized by an alternating layered structure consisting of water and fluid with negative mass density. We propose that an acoustic metamaterial composed of three layers in water background can be designed to replace negative mass density fluid. The effective mass density and bulk modulus of the system that is composed of the acoustic metamaterial and water are dependent on the incident frequency and the geometric size of the acoustic metamaterial. We tune the geometric size of the acoustic metamaterial to approach the corresponding mass density distribution of the negative mass density fluid at a specific frequency. Thereby, the acoustic bending waveguide designed by using transformation acoustics can be achieved by the acoustic metamaterials.     

Passage from spin-polarized surface states to unpolarized quantum well states in topologically nontrivial Sb films

Topological materials have unusual surface spin properties including a net surface spin current protected by the bulk symmetry properties. When such materials are reduced to thin films, their gapless spin-polarized surface states must connect, by analytic continuation, to bulk-derived quantum-well states, which are spin-unpolarized in centrosymmetric systems. The nature of this passage in a model system, Sb films, is investigated. Angle-resolved photoemission shows a smooth transition, while calculations elucidate the correlated evolution of the spin and charge distributions in real space.     

High-power Q-switched laser with high-order Laguerre–Gaussian modes: application for extra-cavity harmonic generations

We present a compact efficient scheme for generation of high-order Laguerre–Gaussian TEM _p,0 modes in a diode-pumped actively Q-switched Nd:YVO₄ laser. The resonator is composed of two plane mirrors with an intracavity concave lens to expand the cavity mode size for generating a high-power Laguerre–Gaussian TEM_5,0 mode. We further confirm that the TEM_5,0 mode is noticeably superior to the TEM_0,0 mode in the processes of second and third harmonic generations.     

Search for the CP-violating decays Upsilon(4S)-->B0B0-->J/psiKS0+J/psi(etac)KS0

We report the first search for CP-violating decays of the Upsilon(4S) using a data sample that contains 535 x 10(6) Upsilon(4S) mesons with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. A partial reconstruction technique is employed to enhance the signal sensitivity. No significant signals were observed. We obtain an upper limit of 4 x 10(-7) at the 90% confidence level for the branching fractions of the CP violating modes, Upsilon(4S)-->B(0)B(0)-->J/psiK(S)(0)+J/psi(eta(c))K(S)(0). Extrapolating the result, we find that an observation with 5sigma significance is expected with a 30 ab(-1) data sample, which is within the reach of a future super B factory.     

Search for B --> h(*)nunu[over ] decays at Belle

We present a search for the rare decays B --> h(*)nunu[over ], where h(*) stands for a light meson. A data sample of 535 x 10{6} BB[over ] pairs collected with the Belle detector at the KEKB e{+}e{-} collider is used. Signal candidates are required to have an accompanying B meson fully reconstructed in a hadronic mode and signal side particles consistent with a single h(*) meson. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The limits on B{0} --> K{*0}nunu[over ] and B{+} --> K{+}nunu[over ] decays are more stringent than the previous constraints, while the first searches for B{0} --> K{0}nunu[over ], pi{0}nunu[over ], rho{0}nunu[over ], varphinunu[over ] and B{+} --> K{*+}nunu[over ], rho{+}nunu[over ] are reported.     

Experimental Investigation of Vapor Chamber Module Applied to High-Power Light-Emitting Diodes

This article experimentally investigates the thermal performance of the vapor chamber module applied to the high-power light-emitting diodes in natural convection. The flat-plate-type vapor chamber and the lamp-type vapor chamber are provided to solve the heat dissipation problem of the high-power light-emitting diodes. The results show that the spreading resistance and the corresponding temperature difference of the flat-plate-type vapor chamber at 30 W are lower than those of the copper plate by 34% and 4°C, respectively, and are lower than those of the aluminum plate by 56% and 6°C, respectively. Compared with the copper and aluminum plates, the lamp-type vapor chamber at 15 W is reduced about 8% and 12% for the total thermal resistance, respectively. In addition, it is also about 3°C and 5°C lower for the central wall temperature of the lighting side, respectively. This study provides a new thermal management method to solve the heat dissipation of the high-power light-emitting diodes. Furthermore, the vapor chamber can effectively lower the spreading resistance and diminish the hotspot effect.     

Fractional programming approach to fuzzy weighted average

This paper proposes a fractional programming approach to construct the membership function for fuzzy weighted average. Based on the -cut representation of fuzzy sets and the extension principle, a pair of fractional programs is formulated to find the -cut of fuzzy weighted average. Owing to the special structure of the fractional programs, in most cases, the optimal solution can be found analytically. Consequently, the exact form of the membership function can be derived by taking the inverse function of the -cut. For other cases, a discrete but exact solution to fuzzy weighted average is provided via an efficient solution method. Examples are given for illustration.     

Self-Power Consumption Research with the Thermal Effects and Optical Properties of the HCRI-BIPV Window System

The building integrated photovoltaics(BIPV) application is one of the main study topics in the sustainable building field.In this paper,the high color rendering index(HCRI)-BIPV window system is developed to be used in the indoor environmental control,whose module material has appeared to be effective in improving the visible transmittance and reducing the absorption.This paper describes the performance of grid-connected HCRI-BIPV window system with 0.75 kWp capacity installed in an office building for a natural ventilation solution.The experimental results indicate that accumulative power generation of the HCRI-BIPV window system is 157.60 WKh during the 7-month experiment period.For consideration of each evaluated factors,the HCRI-BIPV window system not only offers the passive energy situation for its power loading but also improves the indoor thermal environment by natural ventilation.     

Improvement of TDDB reliability, characteristics of HfO2 high-k/metal gate MOSFET device with oxygen post deposition annealing

In this work, influences of oxygen effect on an Hf-based high-k gate dielectric were investigated. A post deposition annealing (PDA) including oxygen ion after high-k dielectric deposition was used to improve reliability of the Hf-based high-k/metal gate device. The basic electrical characteristics of devices were compared with and without the PDA process. Experiment results show that the oxygen PDA did not degrade the drive current and effective oxide thickness of the Hf-based gate devices. In addition, reliability issues such as positive bias instability, negative bias instability and TDDB were also improved by the oxygen PDA significantly. During the TDDB test, the charge trapping was characterized by an in situ charge pumping system, which could make us to understand the variations of interface trap during the reliability stress easily.