Chong Qing Huang

Transmission and Distribution of Optical Field in Prism Coupler

Transmission and distribution characteristics of optical field in prism coupler are studies, and the phase matching function of prism coupler is deduced based on coupled wave theory. It is shown that the stable light field distribution and mode pattern are determined by its own geometric and dielectric parameters, but have nothing to do with the categories of incident light sources. It is also found that the coupling effect would generate between waveguides through evanescent field. Our numerical simulation is based on the finite difference time domain method with perfectly matched layer absorbing boundary condition. The simulation program is compiled in MATLAB. The simulation results are analyzed carefully.

Numerical Analysis and Optimal Design Investigation on Air Duct of Tent Air-Conditioner

According to the structural characteristics of tent air-conditioner, the inner flow mechanism and influence factors on aerodynamic characteristics of the air duct was investigated by using Fluent commercial CFD code. The disadvantages of original air duct were analyzed, several design options were proposed, internal flow characteristics was analyzed by numerical simulation, the optimal solution of air duct structure was fixed. The numerical results show that the air flow rate of optimal air duct run up to 125 m3/ h, increase by 18.9% compared to the original duct.

Electrical Characteristics and Microstructures of Bismuth Titanate Ceramics by Sm3+ Substitution

The electrical properties of Sm-doped bismuth titanate，Bi4-xSmxTi3O12 (BST) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all samples. The P-V hysteresis loops of samples with x=0.4 and 1.2 were characterized by large leakage current, whereas for samples with x=0.6 and 0.8 the P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BST ceramic with x=0.8 were above 20μC/cm2 and 60KV/cm , respectively.

The Impact of Cap Layers on the Structural and Optical Properties of Self-Assembled InAs/GaAs Quantum Dots

Self-assembled InAs/GaAs quantum dots structures with low temperature and high temperature cap layers are grown by meta-organic chemical vapor deposition. The effects of Indium composition of high temperature InGaAs cap layer on the structural and optical properties of quantum dots are investigated by the atomic force microscopy and photoluminescence. Emission peak wavelengths shift from 1218 nm to 1321 nm when the Indium composition of high temperature InGaAs cap layer increase form 0 to 0.17.

MOCVD Growth and Optical Properties of Self-Assembled InAs/GaAs Quantum Dots

InAs/GaAs quantum dots structures are grown by meta-organic chemical vapor deposition. The effects of growth temperatures on the structural and optical properties of quantum dots are investigated by the atomic force microscopy and photoluminescence. An areal density of 9.3×109cm2 and a strongly enhanced photoluminescence intensity are obtained at the temperature of 505°C, furthermore, the low and high growth temperature tend to form coalescent islands and decrease the intensity of photoluminescence spectra.

Study of higher-order modes for waveguide grating coupler

The vector two-dimensional finite difference time domain method is applied to analyze the higher-order modes of waveguide grating couplers (WGCs). The phase matching function of WGC is deduced based on diffraction equation. The stable field distributions and mode patterns of TE1, TE2 and TE3 in WGCs are obtained by using Gaussian beam as a driving source. It is found that the optical mode is determined by grating parameters and waveguide structures. According to the mode field distribution, the optimum coupling efficiency can be predicted, and thus highly-efficient WGCs which are of practical use in integrated optical circuits and optoelectronic devices can be designed conveniently.

Design of Super Narrowband DWDM Filters Based on the Effect of Spectral Splitting

A novel approach is proposed to design super narrowband DWDM Filters consisting of multiple quantum wells (MQWs) by employing photonic crystals. Numerical investigations prove that the closed-cavity MQWs are more suitable for DWDM systems compared with the open-cavity MQWs. It is shown that different confined states could emerge from photonic band gap, which can be used as high-frequency carriers one-to-one. It is also found that these proposed MQWs could split the single spectral lines into multiples based on the effect of spectral splitting, and the number of the splitting is just equal to the number of the wells. In this way, the density of carriers can be increased multiplicatively in the same wave band, and thus the spectral efficiency can be improved multiplicatively. These results provide the prospects of channel density maximization and effective bandwidth optimization for optical communication.

High-resolution Measurement of Refractive Index Based on Resonant Tunneling Effect

A high-resolution measurement device of refractive index with high transmissivity and Q factor based on resonant tunneling effect is presented. The device is constructed by one dimensional photonic crystal (PC) with a defect which would produce different resonant peaks in PC band gap. These peaks are sensitive to the change of the refractive index for different mediums which are filled in the defect. It is found that with a spectrometer that can resolve a resonant peak shift of 0.5nm, at the resonant wavelength of about 1550nm, the resolution of refractive index should be better than Δn = 0.0008, and the transmissivity could be accessible to 1. Both the plane wave method and the finite difference time domain method are employed in numerical analysis. The device is suitable in a variety of applications of practical interest, since many physical, chemical, and biological parameters can be known through measurement of the refractive index.