Dynamical semiconductor medium FDTD simulation of current-injection nanophotonic devices

We report successful simulation of current-injection photonic crystal laser showing the spatial-temporal evolution of the electromagnetic field as well as carrier distribution using our dynamical semiconductor medium (DSM) FDTD model, showing its capability in dealing with complex electromagnetic structures and semiconductor carrier dynamics.     

A generalized 2D FDTD model for photonic crystal fibers with frequency dependent media

A generalized model based on the two-dimensional finite-difference time-domain (2D FDTD) method for photonic crystal fibers (PCF) with frequency dependent media is presented. The Maxwell’s curl equations are formulated using flux density and the magnetic field. Auxiliary differential equations are used with complex-conjugate pole-residue pairs which incorporate the material dispersion of the dispersive media. The model is demonstrated to be a unified approach for arbitrary dispersive materials; therefore, it definitely reduces implementation cost when dealing with different frequency-dependent materials.     

Amplification and photonic band gaps for eigenmodes in two-dimensional photonic crystals with active media

The behavior of eigenmodes near the first low-frequency band gap of a two-dimensional squarearray photonic crystal in the presence of amplification has been studied in detail using an approximate analytic solution for the mode dispersion characteristics. A qualitative analysis of the complex propagation constants was conducted for various directions in the crystal, and the frequency regions corresponding to amplification and absence of transmission due to interference-induced wave damping were identified. The enhancement of amplification in a two-dimensional photonic crystal was estimated.     

Modeling magnetic photonic crystals with lossy ferrites using an efficient complex envelope alternating-direction-implicit finite-difference time-domain method

In this Letter, we present an efficient complex-envelope alternating-direction-implicit finite-difference time-domain (CE-ADI-FDTD) method for the transient analysis of magnetic photonic crystals with lossy ferrites. The proposed CE-ADI-FDTD method is generally formulated for a saturated ferrite with anisotropic permittivity tensor and ferrite loss. Auxiliary differential equations for modeling saturated ferrite and Maxwell's curl equations are first cast into a first-order differential system in a CE form. Then, by using an efficient ADI splitting formulas, the proposed CE-ADI-FDTD method is attained in a very concise form with few and simple right-hand side terms. The performance of the proposed method is validated and compared with the explicit FDTD method.     

Application of fast Pade approximation in simulating photonic crystal nanocavities by FDTD technology

The exact calculation of mode quality factor Q is a key problem in the design of high-Q photonic crystal nanocavity. On the basis of further investigation on conventional Pade approximation, FDM and DFT, Pade approximation with Baker’s algorithm is enhanced through introducing multiple frequency search and parabola interpolation. Though Pade approximation is a nonlinear signal processing method and only short time sequence is needed, we find the different length of sequence requirements for 2D and 3D FDTD, which is very important to obtain convergent and accurate results. By using the modified Pade approximation method and 3D FDTD, the 2D slab photonic crystal nanocavity is analyzed and high-Q multimode can be solved quickly instead of large range high-resolution scanning. Monitor position has also been investigated. These results are very helpful to the design of photonic crystal nanocavity devices.     

等离子体光子晶体的FDTD分析

等离子体光子晶体是等离子体和介质（真空）构成的人工周期性结构.用分段线性电流密度 递归卷积时域有限差分（PLCDRC-FDTD）算法分析了等离子体光子晶体和缺陷等离子体光子 晶体.从时域的角度分析了高斯脉冲在等离子体光子晶体中的传播过程，给出了时域反射和 透射波形.然后，从频域的角度分析了等离子体光子晶体和带缺陷的等离子体光子晶体的电 磁反射系数和透射系数.计算表明，等离子体光子晶体对频率小于等离子体频率的低频电磁 波几乎完全反射，而透射的电磁波则为频率高于等离子体频率的电磁波.在高频，等离子体 光子晶体则出现类似一般光子晶体的光子带隙特性. 关键词： 等离子体 光子晶体 时域有限差分法 等离子体光子晶体     

高阶色散介质的改进移位算子时域有限差分方法

提出一种适用于高阶Debye,Drude,Lorentz及其混合模型的改进移位算子的时域有限差分(SO-FDTD)方法。从介质极化率函数出发,将其写成一阶或二阶有理分式求和的形式,并在随时间步推进计算的过程中,通过引入中间变量和设置临时变量,克服了常规SO-FDTD将高阶模型直接转化为有理分式所导致的计算复杂性和内存占用量大的问题。同时,改进SO-FDTD方法的时域推进计算步骤具有通用性,克服了常规递归卷积(RC-FDTD)方法对各种高阶模型具有不同计算公式,因而不能形成通用计算程序的问题。最后,通过空气-高阶色散介质界面的反射系数计算验证了算法的有效性和通用性。     

高阶色散介质的改进移位算子时域有限差分方法

提出一种适用于高阶Debye,Drude,Lorentz及其混合模型的改进移位算子的时域有限差分(SO-FDTD)方法。从介质极化率函数出发,将其写成一阶或二阶有理分式求和的形式,并在随时间步推进计算的过程中,通过引入中间变量和设置临时变量,克服了常规SO-FDTD将高阶模型直接转化为有理分式所导致的计算复杂性和内存占用量大的问题。同时,改进SO-FDTD方法的时域推进计算步骤具有通用性,克服了常规递归卷积(RC-FDTD)方法对各种高阶模型具有不同计算公式,因而不能形成通用计算程序的问题。最后,通过空气-高阶色散介质界面的反射系数计算验证了算法的有效性和通用性。     

磁化等离子体光子晶体的FDTD分析

磁化等离子体光子晶体是磁化等离子体和介质(真空)构成的人工周期性结构.本文用磁化等离子体的分段线形电流密度卷积(PLCDRC)时域有限差分(FDTD)算法分析了磁化等离子体光子晶体特性.分析了磁化等离子体参数对电磁带隙的影响.从时域的角度分析了高斯脉冲在磁化等离子体光子晶体中的传播过程，给出了时域反射和透射波形.从频域的角度给出了磁化等离子体光子晶体的电磁反射系数和透射系数，并对结果进行了分析. 关键词： 磁化等离子体 光子晶体 时域有限差分法     

GaAs/AlGaAs photonic crystals for VCSEL-type semiconductor lasers

The results of modelling of the influence of photonic crystal on the performance of VCSEL-type semiconductor laser structure are shown and indicate that the use of those structures would significantly improve the working parameters of the devices. The method of fabrication of photonic crystals in the Bragg mirrors of GaAs/AlGaAs-based VCSELs is presented.     

若干新型微纳光子学器件研究

光子晶体和纳米光纤是两种重要的微纳光子学材料,各自具有非常独特的控制光子传输状态的功能,是研究微纳尺度下光与物质相互作用的重要平台,也是实现新型微纳光子学器件的重要基础.文章简要介绍了超快速低功率光子晶体全光开关、纳米光纤传感器、干涉器和介质-金属纳米线复合结构器件的研究进展.     

Improved Dirichlet-to-Neumann map method for modeling extended photonic crystal devices

A typical photonic crystal (PhC) device has only a small number of distinct unit cells. The Dirichlet-to-Neumann (DtN) map of a unit cell is an operator that maps the wave field to its normal derivative on the boundary of the cell. Based on the DtN maps of the unit cells, a PhC device can be efficiently analyzed by solving the wave field only on edges of the unit cells. In this paper, the DtN map method is further improved by an operator marching method assuming that a main propagation direction can be identified in at least part of the device. A Bloch mode expansion method is also developed for structures exhibiting partial periodicity. Both methods are formulated on a set of curves for maximum flexibility. Numerical examples are used to illustrate the efficiency of the improved DtN map method.     

若干新型微纳光子学器件研究

光子晶体和纳米光纤是两种重要的微纳光子学材料,各自具有非常独特的控制光子传输状态的功能,是研究微纳尺度下光与物质相互作用的重要平台,也是实现新型微纳光子学器件的重要基础.文章简要介绍了超快速低功率光子晶体全光开关、纳米光纤传感器、干涉器和介质-金属纳米线复合结构器件的研究进展.     

Study of superluminal-pulse propagation in one-dimensional photonic crystals by the FDTD method

We study the pulse propagation in a one-dimensional photonic crystal using the finite-difference time-domain method. The wave propagation inside the crystal is the result of superposition of forward and backward waves. We observed the superluminal phenomena and negative values of the velocity of the energy-density maximum. The energy velocities within the crystal never exceed the speed of light in vacuum. We hope that our study contributes to a further understanding of the superluminal phenomena.     

FDTD法对二维正方格子光子晶体带隙的数值计算

通过optiFDTD模拟软件对二维椭圆柱构造的正方格子光子晶体的禁带特性进行了数值模拟。分别研究了在空气中椭圆介质(Ge,Si,GaAs)柱和在介质(Ge,Si,GaAs)中椭圆空气柱构造的二维正方格子光子晶体中椭圆柱的横轴半径和纵轴半径的大小,以及椭圆柱的不同旋转角度对光子禁带的影响;并计算出了在上述两种情况下的空气和介质中的最优结构参数。     

一种新的模拟渗流运动的数值方法

根据格子Boltzmann方法及相关理论，建立了一个新的模拟渗流运动的数值模型，所得模型没有在边界上采取相应平均措施，同时还避免了一些非物理副产品的出现-实例计算数值结果与精确解符合较好，证明模型可靠- 关键词： 渗流 格子Boltzmann方法 数值模型     

Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

In this paper, the generalized nonlinear Schr\"{o}dinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton self-frequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.     

二维正方各向异性碲圆柱光子晶体完全禁带中缺陷模的FDTD计算分析和设计

用FDTD方法计算了二维正方晶胞各向异性碲圆柱光子晶体的点缺陷模.为了得到TE,TM模式在完全禁带中具有相同共振频率的缺陷模,对中心点缺陷半径Rd以及中心附近对称位置的点缺陷半径Rn做了一系列微调.计算表明,TM模对于Rn的变化不敏感,而TE模随着Rn的改变出现了明显的规则的移动趋势.通过计算分析,发现对应于f=0.4的背景(R=0.3568a),当Rd=0.55a,Rn=0.26a时在完全禁带中TE和TM的缺陷模具有相同的共振频率ω0=0.2466ωe(其中ωe=2πca,a为晶格常数) 关键词： 时域有限差分法 光子晶体 缺陷模 各向异性     

Quantum dot photonic devices for lightwave communication

For InAs-GaAs based quantum dot lasers emitting at 1300 nm digital modulation showing an open eye pattern up to 12 Gb/s at room temperature is demonstrated, at 10 Gb/s the bit error rate is below 10^-12 at -2 dBm receiver power. Cut-off frequencies up to 20 GHz are realised for lasers emitting at 1.1 m. Passively mode-locked QD lasers generate optical pulses with repetition frequencies between 5 and 50 GHz, with a minimum Fourier limited pulse length of 3 ps. The uncorrelated jitter is below 1 ps. We use here deeply etched narrow ridge waveguide structures which show excellent performance similar to shallow mesa structures, but a circular far field at a ridge width of 1 m, improving coupling efficiency into fibers. No beam filamentation of the fundamental mode, low -factors and strongly reduced sensitivity to optical feedback is observed. QD lasers are thus superior to QW lasers for any system or network.Quantum dot semiconductor optical amplifiers (QD SOAs) demonstrate gain recovery times of 120–140 fs, 4–7 times faster than bulk/QW SOAs, and a net gain larger than 0.4 dB/(mm*QD layer) providing us with novel types of booster amplifiers and Mach–Zehnder interferometers.These breakthroughs became possible due to systematic development of self-organized growth technologies. PACS 81.07.Ta; 81.16.Dn; 42.55.Px; 42.60.-v     

Quantum Boltzmann equation solved by Monte Carlo method for nano-scale semiconductor devices simulation

A two-dimensional (2D) full band self-consistent ensemble Monte Carlo (MC) method for solving the quantum Boltzmann equation, including collision broadening and quantum potential corrections, is developed to extend the MC method to the study of nano-scale semiconductor devices with obvious quantum mechanical (QM) effects. The quantum effects both in real space and momentum space in nano-scale semiconductor devices can be simulated. The effective mobility in the inversion layer of n and p channel MOSFET is simulated and compared with experimental data to verify this method. With this method 50nm ultra thin body silicon on insulator MOSFET are simulated. Results indicate that this method can be used to simulate the 2D QM effects in semiconductor devices including tunnelling effect.