Electrical and Optical Coupling in an Electroabsorption Modulator Integrated With a DFB Laser

Electrical and optical coupling in an electroabsorption (EA) modulator integrated with a distributed feedback (DFB) laser have been investigated. The integrated device is treated as a three-port optoelectronic device with two electrical ports and one optical output port. The scattering parameters of this three-port device have been measured in the designed experiment. The measured results indicate that there exists the electrical coupling between the DFB laser and EA modulator of the integrated light source whenever the current applied to the laser section is below or above the threshold current, and the optical coupling will have stronger influence on the frequency responses than the electrical coupling when the bias current is above the threshold. A small-signal equivalent circuit model for the integrated device is established considering both the electrical and internal optical coupling. Experiments show that the equivalent circuit model is reasonable and the determined element values are correct. Based on the measurement and modeling, the influences of the electrical and optical coupling on the high-frequency responses are investigated and the effective measure to eliminate the additional modulation in the DFB laser are discussed.     

考虑增益饱和及寄生参数的LD的模拟分析

基于包含增益饱和项的半导体激光器速率方程,分析了增益饱和因子和寄生参数对DFB激光器的动态特性的影响.建立了激光器用于数值计算的Simulink模型,对激光器的调制响应进行了数值分析;结合电子电路的特点,建立了一种考虑寄生参量的小信号等效电路模型,该模型将速率方程表征为由线性电路元件组成的电路模型;采用Matlab和PSpice两种软件模拟了该激光器的调制响应.结果表明张弛振荡频率和调制带宽随偏置电流的增加而增加,而增益饱和因子和寄生参数的存在使谐振频率衰减和带宽降低,同时也证明了所建模型的准确性和适用性.为改善DFB激光器的动态特性及优化设计器件结构参数提供了理论依据.     

电吸收调制器和DFB激光器集成器件的测量

提出了一种测量电吸收调制器和激光器集成器件芯片散射参数的新方法.根据电吸收调制器和封装寄生参数的等效电路模型,对测量的反射系数进行拟合,得到封装寄生参数和电吸收调制器的等效电路元件的参数值.通过分析发现测试封装寄生参数对电吸收调制器的测试结果有很大影响.去除了封装寄生参数的影响后,得到了调制器的反射和传输参数的真实频响特性     

太赫兹平面肖特基二极管参数模型

根据太赫兹平面肖特基二极管物理结构,在理想二极管SPICE参数模型的基础上建立了二极管小信号等效电路模型。依据该二极管等效电路模型设计了基于共面波导（CPW）去嵌方法的二极管S参数在片测试结构,并对其在0.1~50 GHz、75~110 GHz频率范围内进行了高频小信号测试,利用测试结果提取了高频下二极管电路模型中各部分电容、电阻以及电感参数。将相应的高频下电容与电阻参数分别与低频经验公式电容值和直流I-V测试提取的电阻值进行了对比,并利用仿真手段对高频参数模型进行了验证。完整的参数模型以及测试手段相较于理想二极管SPICE模型和传统的参数提取方法可以更为准确地表征器件在高频下的工作状态。该建模思路可用于太赫兹频段非线性电路的优化设计。     

Very high-frequency small-signal equivalent circuit for shortgate-length InP HEMTs

A small-signal equivalent circuit for short gate-length InP high electron-mobility transistors (HEMTs) operating at very high frequency (HF) is proposed. First, the extrinsic parameters of the equivalent circuit are determined using a cold HEMT, but without forward gate bias. Then the intrinsic parameters of the equivalent circuit are extracted, including the frequency dependence of some of them. A fast and accurate method based on least-squares regressions is presented to obtain the extrinsic and intrinsic parameters from measured S-parameters. The improved equivalent circuit accurately fits the S-parameters of 0.25-μm InP HEMTs over the 500-MHz up to 40-GHz measurement bandwidth, for all gate-to-source and drain-to-source voltages     

A simple and analytical parameter-extraction method of a microwaveMOSFET

A simple and accurate parameter-extraction method of a high-frequency small-signal MOSFET model including the substrate-related parameters and nonreciprocal capacitors is proposed. Direct extraction of each parameter using a linear regression approach is performed by Y-parameter analysis on the proposed equivalent circuit of the MOSFET for high-frequency operation. The extracted results are physically meaningful and good agreement has been obtained between the simulation results of the equivalent circuit and measured data without any optimization. Also, the extracted parameters, such as g_m and g_ds, match very well with those obtained by DC measurement     

Precise measurement of semiconductor laser chirp using effect ofpropagation in dispersive fiber and application to simulation oftransmission through fiber gratings

Measurements of small-signal intensity modulation from direct-modulated distributed feedback (DFB) semiconductor lasers after propagation in dispersive fiber have previously been used to extract intrinsic laser chirp parameters such as linewidth enhancement factor and crossover frequency. Here, we demonstrate that the simple rate equations do not satisfactorily account for the frequency response of real DFB lasers and describe some experimental techniques that conveniently determiner the precise laser chirp. Implications for simulation of high-speed lightwave systems are also considered     

High performance modules of 2.5 Gbps modulator integrated DFBlasers using new RF impedance matching technique

We report the improvement of frequency response characteristics of 2.5 Gbps modulator integrated distributed feedback (MI-DFB) laser modules using new impedance matching technique. Frequency responses for the fabricated module using the `+' shaped microstrip line for impedance matching have been significantly improved such as the RF return loss of 11 dB and the 3 dB frequency bandwidth of 4.1 GHz, compared to 6 dB return loss and 1.5 GHz bandwidth for the conventional module. These results can also be predicted by the simulation of frequency responses for the modules, From the fabricated MI-DFB laser modules, good transmission performance has been obtained up to 640 km     

基于等效电路模型的半导体激光器直流偏置分析

从传统的激光器速率方程出发,同时考虑芯片封装寄生参量和本征区接触参量的影响,得出一种双异质结半导体激光器的新型等效电路模型,在此模型基础上用电路仿真软件PSpice分析了直流偏置对激光器弛豫振荡、小信号频率响应、大信号脉冲响应的影响。     

Modeling of quantum-well lasers for computer-aided analysis ofoptoelectronic integrated circuits

A two-port circuit model for quantum-well (QW) lasers has been developed from rate equations. With emphasis on the physical principles, the phenomena of the recombination process of electron-hole pairs and the light wave resonance in the active region have been incorporated into this new model. The model has been implemented in a circuit simulator and validated with measured DC and transient laser characteristics. The frequency effects on the modulation properties of QW lasers have been studied and analyzed using a small-signal model. Simulation results show excellent agreement with experimental data     

Simulation of SiGe:C HBTs using neural network and adaptive neuro-fuzzy inference system for RF applications

In this article, the small-signal equivalent circuit model of SiGe:C heterojunction bipolar transistors (HBTs) has directly been extracted from S-parameter data. Moreover, in this article, we present a new modelling approach using ANFIS (adaptive neuro-fuzzy inference system), which in general has a high degree of accuracy, simplicity and novelty (independent approach). Then measured and model-calculated data show an excellent agreement with less than 1.68?×?10^?5% discrepancy in the frequency range of higher than 300 GHz over a wide range of bias points in ANFIS. The results show ANFIS model is better than ANN (artificial neural network) for redeveloping the model and increasing the input parameters.     

Small-signal model parameter extraction of E-mode N-polar GaN MOS-HEMT using optimization algorithms and its comparison

An improved small-signal parameter extraction technique for short channel enhancement-mode N-polar GaN MOS-HEMT is proposed,which is a combination of a conventional analytical method and optimization techniques.The extrinsic parameters such as parasitic capacitance,inductance and resistance are extracted under the pinch-off condition.The intrinsic parameters of the small-signal equivalent circuit (SSEC) have been extracted including gate forward and backward conductance.Different optimization algorithms such as PSO,Quasi Newton and Firefly optimization algorithm is applied to the extracted parameters to minimize the error between modeled and measured S-parameters.The different optimized SSEC models have been validated by comparing the S-parameters and unity current-gain with TCAD simulations and available experimental data from the literature.It is observed that the Firefly algorithm based optimization approach accurately extracts the small-signal model parameters as compared to other optimization algorithm techniques with a minimum error percentage of 1.3％.     

片式电容器分布参数测算方法的研究

采用矢量网络分析仪测量片式电容器的S参数、射频电路设计模拟仿真软件和Y参数二端口网络模型提取等效串联电路的C、L、R参数,研究了片式电容器在射频电路中的分布参数,并由此计算出不同频率下片式电容器的Q值。结果表明:该方法能够准确地得出片式电容器在射频电路中的分布参数,并能反映出片式电容器的频率特性。     

Characterization of Parasitics in TO-Packaged High-Speed Laser Modules

An elaborate analysis of the parasitic network of high-speed through-hole packaging (TO)-type laser modules is presented using a small-signal equivalent circuit model. The intrinsic laser diode is obtained using the optical modulation technique, and is embedded into the model as a separate component. Three step-by-step measurements are made for determining the packaging parasitic network, including the test fixture, TO header, submount, bonding wire, and parasitics of the laser chip. A good agreement between simulated and measured results confirms the validation and accuracy of the characterization procedures. Furthermore, several key parasitic elements are found based on the simulation of the high-frequency responses of the packaged devices. It is expected that the 3-dB bandwidth of 12 GHz or more of the low-cost TO packaged laser module may be achieved using the proposed optimization method     

考虑速度过冲效应的HEMT物理模型

本文提出了一种考虑这冲效应的ＨＥＭＴ器件静态和小信号解析物理模型。通过对栅极下面道中造近源端附近的电场采用弱强梯场近似，提出了一个半经验的速度过冲模型，在非线性电荷控制模型的基础上述导出了基于物理参数的ＨＥＭＴ器件电流－电压特性和小等效电路参数的解析表达式。实际计算结果与测得数据比较表明，本模型具有比较高的精度。     

Subthreshold parameters of radio-frequency multi-finger nanometer MOS transistors

The subthreshold radio-frequency (RF) characteristics of multi-finger nanoscale MOS transistors were studied by using the measured scattering (s) parameters. Small-signal circuit parameters were determined based on a simplified small-signal equivalent circuit model. We found that besides the source and gate resistances, most of the parameters such as the channel resistance, drain inductance and intrinsic capacitance are found to be significantly different to those in the saturation mode of operation. The subthreshold channel resistance increases and the drain inductance decreases as the finger number increases because of the more significant charge transport along the finger boundaries. In addition, the channel resistance can be governed by the drain-induced barrier lowering in a transistor with very short gate length. The equivalent intrinsic capacitance of the small-signal equivalent circuit is governed by the substrate resistance and capacitance which make the parameter extraction more difficult.     

Circuit modeling of the effect of diffusion on damping in a narrow-stripe semiconductor laser

This paper describes a circuit modeling technique for directly modulated narrow-stripe semiconductor lasers with strong carrier confinement and index guiding. It is shown that diffusion damping of the modulation response, due to a nonuniform electron density distribution in the active layer, can be accounted for in terms of an equivalent optical gain saturation. Based on this equivalence, a small-signal ac circuit model of a narrow-stripe laser is derived. The model can be used to determine the intensity modulation and frequency modulation response characteristics of a packaged device.     

一种改进的用于SiGe HBT的焊盘模型参数提取技术

提出了一种适用于Si基器件的焊盘寄生参数的提取方法,并将此方法提取的焊盘寄生参数结果与用近似法提取的焊盘寄生参数结果的精度作了比较。比较结果表明,文中提出的线性拟合法精度较高。焊盘寄生参数提取并剥离后,对AMS 0.35μm BiCMOS工艺加工的SiGe HBT的小信号等效电路进行参数提取,其中,外部电阻用基极"过驱动电流"法提取,本征参数用分析法提取,将参数提取结果代入模型进行仿真,仿真得到的S参数在整个测试频率范围内均与测试结果吻合良好。     

Equivalent circuit models for resonant and PWM switches

The nonlinear switching mechanism in pulsewidth-modulated (PWM) and quasi-resonant converters is that of a three-terminal switching device which consists only of an active and a passive switch. An equivalent circuit model of this switching device describing the perturbations in the average terminal voltages and current is obtained. Through the use of this circuit model the analysis of pulsewidth modulated and quasiresonant converters becomes analogous to transistor circuit analysis where the transistor is replaced by its equivalent circuit model. The conversion ratio characteristics of various resonant converters and their relationship to a single function, called the quasi-resonant function, is easily obtained using the circuit model for the three-terminal switching device. The small-signal response of quasi-resonant converters to perturbations in the switching frequency and input voltage is determined by replacing the three-terminal switching device by its small-signal equivalent circuit model     

Analysis of device parameters for pnp-type AlGaAs/GaAs HBTsincluding high-injection using new direct parameter extraction

Device parameters of the small-signal T equivalent circuit for pnp-type AlGaAs/GaAs heterojunction bipolar transistors (HBTs) are obtained using a new direct parameter extraction technique. These parameters are analyzed not only under the low-current conditions but also under high-current conditions so as to understand the RF-performance fall-off after base pushout occurs. In this analysis, the intrinsic and extrinsic small-signal parameters which affect RF performance are directly determined using several steps without numerical optimization in order to properly analyze device parameters. The T equivalent circuit model determined by the method shows excellent agreement with the mean errors of 3.5-6.9% under both low-and high-current conditions. The analysis showed that the intrinsic transit time, which is the sum of the base transit time (τ_b) and the collector depletion layer transit time (τ_c), small-signal emitter resistance (r_e), small-signal base resistance (r_b) and collector-base capacitance (C_BC) all increase under high-current conditions. In addition, we found that the intrinsic transit time is the dominant parameter for the fall-off of the cut-off frequency (f_t) under high-current conditions, and there is little effect of r_b and C_BC in the fall-off of the maximum oscillation frequency (f_max) under high-current conditions. Judging from these results, device parameters are successfully obtained under a wide current range by a new parameter extraction technique and circuit modeling for HBTs under a wide current range can be achieved using the small-signal T-equivalent circuit