An equivalent circuit model for terahertz quantum cascade lasers:Modeling and experiments

Terahertz quantum cascade lasers(THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In order to illustrate the capability of the model, the steady and dynamic performances of the fabricated THz QCLs are simulated by the model.Compared to the sophisticated numerical methods, the presented model has advantages of fast calculation and good compatibility with circuit simulation for system-level designs and optimizations. The validity of the model is verified by the experimental and numerical results.     

Nonlinear circuit model for semiconductor lasers

The multimode rate equations are transformed to the circuit equations of the electro-optical system by expressing the charge carrier concentrations and recombination rates in terms of voltage across the active layer, and representing the photon densities of the respective modes by a set of voltages. By proper approximation of functions describing the recombination rates, the equivalent circuit can be composed of conventional linear and nonlinear circuit components.     

SiGe HBT大信号等效电路模型

基于SiGe HBT(异质结双极晶体管)的物理模型，建立了描述SiGe HBT的大信号等效电路模型.该等效电路模型考虑了准饱和效应和自热效应等，模型分为本征和非本征两部分，物理意义清晰，拓扑结构相对简单.该模型嵌入了PSPICE软件的DEVEO(器件方程开发包)中.在PSPICE软件资源的支持下，利用该模型对SiGe HBT器件进行了交直流特性模拟分析，模拟结果与理论分析结果相一致，并且与文献报道的结果符合较好. 关键词： SiGe HBT 等效电路模型 PSPICE     

An equivalent circuit model of a novel photodetector

An equivalent circuit model of a novel photodetector (PD) is proposed in this article. We use this model to describe the relation between the bias voltage and current (I–V), also the bias voltage and capacitance(C–V) of this kind of novel PD. The circuit model could optimize the structure of the circuit and could be linked with the readout circuit. According to the comparison between the simulation result and the experimental result by circuit testing, we could find they are in good agreement, which proving the correctness of the equivalent circuit model. The signification of this equivalent circuit model is to design an optimal readout circuit (ROIC) for the novel PD.     

Phase-locked mutually coupled 1.3 microm quantum-dot lasers

Fabry-Perot InAs quantum-dot lasers grown on GaAs substrates are mutually coupled with a delay of several nanoseconds. Stable phase-locked output with narrow linewidth is obtained when the frequency detuning between the two lasers is less than 4 GHz. This simple locking scheme could find application in a variety of photonics applications.     

Threshold flux-controlled memristor model and its equivalent circuit implementation

Modeling a memristor is an effective way to explore the memristor properties due to the fact that the memristor devices are still not commercially available for common researchers. In this paper, a physical memristive device is assumed to exist whose ionic drift direction is perpendicular to the direction of the applied voltage, upon which, corresponding to the HP charge-controlled memristor model, a novel threshold flux-controlled memristor model with a window function is proposed. The fingerprints of the proposed model are analyzed. Especially, a practical equivalent circuit of the proposed model is realized, from which the corresponding experimental fingerprints are captured. The equivalent circuit of the threshold memristor model is appropriate for various memristors based breadboard experiments.     

An equivalent circuit model for microwave-biased extrinsic photoconductors1

An equivalent circuit model for microwave-biased extrinsic photoconductors is introduced. Theoretical performance results calculated from the model are compared to experimental values of a microwave-biased mercury-doped germanium photoconductor operating at high background photon irradiance levels. The comparison indicates that the equivalent circuit model is adequate to describe the performance of microwave-biased extrinsic photoconductors. Experimental and theoretical results indicate that microwave-biased extrinsic photoconductors are high gain (G ∼10⁴) devices with a simultaneous submicrosecond speed of response.     

Sensitivity of quantum-dot semiconductor lasers to optical feedback

The sensitivity of quantum-dot semiconductor lasers to optical feedback is analyzed with a Lang-Kobayashi approach applied to a standard quantum-dot laser model. The carriers are injected into a quantum well and are captured by, or escape from, the quantum dots through either carrier-carrier or phonon-carrier interaction. Because of Pauli blocking, the capture rate into the dots depends on the carrier occupancy level in the dots. Here we show that different carrier capture dynamics lead to a strong modification of the damping of the relaxation oscillations. Regions of increased damping display reduced sensitivity to optical feedback even for a relatively large alpha factor.     

压电换能器等效模型分析与阻抗匹配设计

声光可调滤光器(Acousto-optic tunable filter,AOTF)的衍射效率不仅与功率信号源的质量、声光晶体氧化碲(TeO_2)的切型有关,而且压电超声换能器的结构以及其阻抗匹配网络也对AOTF的衍射效率有很大影响。本文对X切型铌酸锂(LiNbO_3,LN)四层镀膜压电超声换能器的等效模型进行了分析,确定了声光介质存在时换能器的阻抗特性,利用射频微波仿真软件,设计了电感-电容复合匹配网络。将换能器压合在TeO_2上,用复色光作为光源进行了声光衍射实验,经仿真与实验验证表明,该匹配电路可以有效的改善压电换能器的阻抗特性,提高换能器带宽,提高能量传输效率,AOTF衍射效率最高可达92.67%。     

用电路模型等效变换的方法教学RL暂态过程

教学RL回路的暂态过程时,为了改善学生对已有知识记忆的激活和建立意义明确的关联,本文使用电路模型等效变换和构建的方法,分别以初态和终态为参考状态,对RL回路的全状态响应进行了分析,直观地将此暂态过程解析为:1)从初态到终态的常系数衰减过程,2)零输入响应和零状态响应的叠加.从而实现对教学效果的提高.     

利用等效电路模型计算耦合腔行波管注-波互作用

通过研究Curnow等效电路模型,得到进行单腔计算的矩阵方程,进而获得线路场方程, 结合运动方程和空间电荷场方程,从而推导出耦合腔行波管一维注波互作用非线性理论模型. 该理论能计算任意的切断、跳变、渐变等结构以及多信号模拟.利用该理论编制的软件计算了 59 GHz-64 GHz耦合腔行波管AM-PM相位失真,三阶互调以及五阶互调分量. 同时模拟得到了59 GHz-64 GHz带内饱和输出功率分布,理论结果与热测结果误差在5%以内.     

Output characteristics of pulsed and continuous-wave-excited quantum-dot microcavity lasers

In the rapidly evolving field of quantum-dot-based microcavity lasers the device characterization is of great importance. In this Letter, we study how information can be obtained from the input/output curve by using a microscopic laser theory for the coupled cavity-quantum-dot system. Semiconductor effects such as a nonlinear source term of spontaneous emission, Pauli blocking, and the absence of complete carrier inversion lead to significant deviations from atomic systems. Especially for pulsed excitation, saturation effects have a tremendous impact on the input/output characteristics and render a simple determination of the spontaneous emission coupling beta impossible.     

The equivalent circuit of a powder electroluminescent capacitor

An electrical equivalent circuit is proposed and analyzed for capacitors filled with powdered ZnS electroluminescent phosphor in the insulator. The basic laws of the behavior of the dielectric characteristics of the specimen in the dark and when illuminated by ultraviolet (UV) light are explained: the existence and properties of a dark frequency maximum of tg and the corresponding dispersion of capacitance C as well as the appearance of certain new maxima tg with UV illumination and their properties. The dark maximum of tg is ascribed to the conductivity of the second phase and the light ones to the photoconductivity of the nonuniform grains. The case of possible negative changes in tg and when the specimen is illuminated by UV light is also considered.A study was made in [1] of the dielectric properties of ZnS phosphor uniformly distributed in a teflon film. Measurements were carried out in weak fields when the processes associated with electroluminescence do not appear. As distinct from photophosphors, a frequency maximum of tg was found in the majority of specimens of ZnS in the dark, with a dispersion of capacitance in its region. The frequency of these photo-maxima () increased with increase in the intensity of UV illumination, and decreased with the lapse of time after cutting off the excitation. Infrared illumination shifts the light maxima to the left along the frequency axis and does not affect the dark maximum of tg at all. It is shown in [1] that this dark maximum is governed by the conductivity of the second phase, and the light maxima by the nonuniform photoconductivity in the natural grains of the phosphor. In certain specimens the conductivity of the second phase increases with temperature and in others it is unchanged. Based on [2], it was concluded that this is connected with differing content of extra-stoichiometric granules.In conclusion the author wishes to express her appreciation of F. I. Vergunas' guidance in the work.     

Analytical framework of small-gap photoconductive dipole antenna using equivalent circuit model

A compact planar antenna sources with on-chip fabrication and high directivity in order to achieve large depth-of-field for better image resolution is the prospective demand for THz imaging application. Therefore, the small-gap photoconductive dipole antennas have been explored to fulfil such applications demand. However, there are certain modalities for improving the photoconductive dipole antenna performance which need to identify to accomplish high THz average radiated power and improved total efficiency. The unit-cell small-gap photoconductive dipole antenna radiation power enhancement methods need to optimize the design parameters with photoconductive material selection from theoretical simulation. Further, the potential improvement of coupling efficiency of THz wave with air as well as femto-second laser incident efficiency is also important parameters to enhance the radiation power of small-gap photoconductive dipole antenna. In this paper, we have presented an analytical procedure employing explicit mathematical expression leading to the physical behaviour of small-gap photoconductive dipole antenna. The effects of biased lines on the antenna performance parameters are discussed with the help of proposed equivalent circuit model. We have explored the effect of gap-size on the THz radiated power and on total radiation efficiency from the proposed photoconductive dipole antennas.     

High-power passively mode-locked tapered InAs/GaAs quantum-dot lasers

We report picosecond pulse generation with high peak power in the range of 3.6 W from monolithic passively mode-locked tapered quantum-dot laser diodes, exhibiting low divergence and good beam quality. These results were achieved using a gain-guided tapered laser geometry. The generation of picosecond pulses with high average power up to 209 mW directly from such tapered lasers is also demonstrated, corresponding to 14.2 pJ pulse energy (14.65 GHz repetition rate). A comparison between the mode-locking performance of these tapered lasers incorporating either five or ten layers of InAs/GaAs self-organized quantum dots in their active layer is also presented.     

An equivalent circuit model for the long-wavelength quantum well infrared photodetectors

We present an equivalent circuit model for AlGaAs/GaAs long wavelength quantum well infrared photodetectors (LW-QWIPs). Bias dependence of the dark current and photoresponse is described with the aid of analogue circuit modeling technique in the TINA software. This model can be integrated with the readout circuit for the whole device circuit simulation and optimization further. The designed parameters of the LW-QWIPs can be fed into this model as user-defined circuit parameters to simulate the detector performance. The obtained results are consistent with the experimental measurements.     

等效回路法在离子液体电极效应中的应用

利用等效电回路模型简化离子液体的电极系统,分析了电极效应中出现的3个特征频率和各自表征的物理意义.基于离子液体介电谱实验数据,获取了等效电回路的基本参数:本体电容、本体电阻和电双层电容,进而得到离子液体样品和电双层的基本介电参数,以及与离子迁移相关的物性参数如扩散系数、迁移率、离子液体中有效离子浓度,对深入理解离子液体导电和界面机制有重要的意义.     

螺旋型爆磁压缩脉冲功率源模拟计算

 以间接馈电的两级螺旋型爆磁压缩发生器为初始功率源，基于等效电路模型，编制了一个螺旋型爆磁压缩脉冲功率源计算程序BCYSSYS。利用该程序对04型爆磁压缩发生器驱动电感负载进行了计算，并将计算结果与实验结果进行比较，两者基本吻合；对该发生器驱动电容负载进行了计算。同时利用铜金属丝电爆炸过程中电阻率与比作用量的关系数据表，对爆磁压缩发生器驱动含电爆炸丝断路开关的电感储能脉冲功率调节系统进行了数值计算。