半导体微腔激光器瞬态响应及调制特性分析

针对半导体微腔激光器的结构特点,考虑到腔量子电动力学中自发辐射增强效应,采用传统速率方程的表示形式,建立了微腔激光器的速率方程,着重讨论了微腔激光器的瞬态响应及调制特性,给出了其动态特性的仿真结果,分析了自发辐射因子、注入电流和腔长对微腔激光器的激射阈值、延迟时间、驰豫振荡频率和光输出等参量的影响,从而为改善微腔激光器的高频调制特性和优化器件结构提供了理论依据.     

数值研究大功率激光器的大电流调制特性

本文对大功率激光器的大信号调制特性进行了分析。由于激光的弛豫振荡行为,会产生瞬态响应。在不同宽度的光限制层的条件下,对量子阱激光器的传输带宽进行了对比。光限制层越宽,载流子的传输效应越明显,导致传输带宽减小。大信号调制下,随着调制深度的增加激光峰值不断变尖锐。随着偏置信号的增大,光子密度也不断增大。     

微腔效应对于1.3μm量子点光子晶体纳腔激光器调制响应的影响（英文）

微腔效应可以提高自发辐射速率,从而起到有效的改善响应调制速率的作用.然而,对于1.3μm GaAs/InAs量子点光子晶体激光器而言,调制速率还会受到复杂的载流子动力学以及更近的空穴能级间隔的影响.因此基于全路径载流子弛豫动力学方程,计算并讨论了腔品质因子(Q)对于阈值和响应调制特性的影响.计算结果表明,高的Q值能够明显改善量子点光子晶体激光器的阈值,但是同时快速增长的光子寿命会导致调制带宽的恶化.所以,存在一个优化的Q值(2500)可以获得超过100 GHz的调制带宽,而当Q值为7 000时,对应的能量传输损耗最低.因此,在量子点光子晶体纳腔激光器的设计中,更全面的考虑各方面的因素对器件的性能的影响,对于获得高速调制低功耗的量子点激光器器件是十分有意义的.     

半导体微腔激光器瞬态响应及调制特性分析

针对半导体微腔激光器的结构特点,考虑到腔量子电动力学中自发辐射增强效应,采用传统速率方程的表示形式,建立了微腔激光器的速率方程,着重讨论了微腔激光器的瞬态响应及调制特性,给出了其动态特性的仿真结果,分析了自发辐射因子、注入电流和腔长对微腔激光器的激射阈值、延迟时间、驰豫振荡频率和光输出等参量的影响,从而为改善微腔激光器的高频调制特性和优化器件结构提供了理论依据。     

微腔效应对于1.3μm量子点光子晶体纳腔激光器调制响应的影响

微腔效应可以提高自发辐射速率,从而起到有效的改善响应调制速率的作用。然而,对于1.3 μm GaAs/InAs量子点光子晶体激光器而言,调制速率还会受到复杂的载流子动力学以及更近的空穴能级间隔的影响。因此本文中我们基于全路径载流子弛豫动力学方程,计算并讨论了腔品质因子（Q）对于阈值和响应调制特性的影响。计算结果表明,高的Q值能够明显改善量子点光子晶体激光器的阈值,但是同时快速增长的光子寿命会导致调制带宽的恶化。所以,存在一个优化的Q值（2500）可以获得超过100GHz的调制带宽,而当Q值为7000时,对应的能量传输损耗最低。因此,在量子点光子晶体纳腔激光器的设计中,更全面的考虑各方面的因素对器件的性能的影响,对于获得高速调制低功耗的量子点激光器器件是十分有意义的。     

隧穿注入量子点激光器概述

介绍了一种新型的载流子隧穿注入量子点激光器,具体内容涉及量子点激光器研究现状、存在的问题、隧穿注入量子点激光器的工作原理和优势、研究现状等。采用隧穿注入这一新的载流子注入方式,可有效提高量子点激光器的温度特性和高频调制特性。     

强光注入锁定半导体激光器的理论分析

通过速率方程建立了强光注入半导体激光器的理论模型,研究了注入光强与从激光器注入锁定频率范围的关系.结果表明,强光注入增大了半导体激光器的注入锁定范围.同时对半导体激光器进行了时间特性的数值模拟,计算结果表明,无论是强光注入还是弱光注入,激光器的输出最终都趋于稳定,通过强光注入锁定条件与弱光注入条件下的对比,得出强光注入能有效地抑制弛豫振荡,缩短达到稳定的时间.     

多量子阱半导体激光器的瞬态响应特性分析

根据光增益与载流子密度的对数关系,在受激发射速率中分别引入了增益饱和项和载流子复合项,通过适应于多量子阱激光器的速率方程,从理论上证明了短腔结构存在与阈值电流最小值对应的最佳阱数。给出了多量子阱激光器的瞬态呼应特性的直接仿真结果及相图,分析了注入电流、阱数和腔长对其激射阈值、开关延误时间、弛豫振荡频率和光输出等能量的影响。     

光纤影响量子点激光器的运行状态数学模型研究

光纤影响下的量子点激光器运行状态具有非线性,构建基于势能函数分析和双态QDL激子模型的光纤影响量子点激光器的运行状态数学模型。在光纤注入状态下,分析量子点激光器的非线性动力学参数模型,结合非线性动力学态的分布和演化特性,利用时间序列、功率谱及相图分析的方法,在不同参数注入下进行量子点激光器的参数空间及运行状态动力学分布特性分析。以光学能级、光学限制因子以及光学增益因子等为约束参数,进行自由运行状态下的量子点激光器基态和激发态特性分析,实现光纤影响下量子点激光器的运行状态数学模型构建。实验结果表明,该模型能有效获取量子点激光器的最优微波线宽,在电流增加的过程中,自由运行光谱能级谱检测性能较好,研究结果为光纤网络互联和光存储提供理论基础。     

太赫兹量子级联激光器光注入特性

基于三能级速率方程,研究了独立运行、主从注入和相互注入太赫兹量子级联激光器(THz-QCLs)的相对强度噪声和调制特性。在自由运行情况下,THz-QCL的自发辐射噪声在低频时表现出白噪声特性。与传统的半导体激光器不同,在低频区没有对应于弛豫振荡的共振峰。主从注入可以有效降低THz-QCLs噪声20 dB,提高THz-QCLs低噪声工作的效率。对于互注入THz-QCLs,即使在锁相区,噪声也明显高于自由运行情况。通过应用注入锁定方案,与直接调制方案相比,可以大大增加调制带宽。     

Direct Modulation Characteristics of Composite Resonator Vertical-Cavity Lasers

We report the small-signal modulation characteristics of a monolithic dual resonator vertical cavity surface emitting laser. The modulation response is described by a system of rate equations with two independent carrier populations and a single longitudinal optical mode. The independent optical overlaps and differential gains of the two active regions can each be adjusted to maximize the output response. We show that under certain conditions, the composite resonator may achieve a higher bandwidth than a single cavity laser with the same photon density. We find the relaxation oscillation frequency to depend mainly on the total photon density and not the individual currents in the two cavities. With appropriate current injection, the composite resonator laser achieves a maximum -3-dB bandwidth of 12.5 GHz and a maximum modulation current efficiency factor of approximately 5GHz/ma^1/2      

Observation and Modeling of a Room-Temperature Negative Characteristic Temperature 1.3-μm p-Type Modulation-Doped Quantum-Dot Laser

A room-temperature negative characteristic temperature (T₀ ) and ultralow threshold current density (J_th) of 48 Amiddotcm^-2 are demonstrated for a 1.3-mum InAs quantum dot laser. These characteristics are obtained by combining a high-growth-temperature GaAs spacer layer with p-type modulation doping of the quantum dots in multiple layer dot-in-a-well structures. Through a comparison of p-doped and undoped devices, a photon coupling mechanism is proposed to account for the different temperature dependences of Jth for the two devices. Numerical simulations based on a rate equation model, which includes photon coupling between ground and excited quantum dot states, are performed. The simulations are able to account for the very different temperature-dependent Jth behavior of the doped and undoped device     

Relaxation oscillations of quantum dot lasers

The relaxation oscillation frequency of quantum dot lasers is modelled theoretically. Its dependency on the driving current, maximum gain, intersublevel relaxation time and homogeneous broadening is investigated. For suitable, feasible quantum dot laser parameters, relaxation oscillation frequencies up to 10 GHz are predicted. Making these devices useful for 5 Gbit/s communication systems     

GaAs/InGaAs量子点探测器件微光读出研究

GaAs/InGaAs量子点光电探测器,在633 nm激光辐射3.5 nW条件下,器件偏压-1.4 V时,测得响应电流8.9×10-9A,电流响应率达到2.54 A/W,量子注入效率超过90%。基于GaAs/InGaAs量子点光电探测器的高量子注入效率、高灵敏度等特点,采用具有稳定的电压偏置,高注入效率和低噪声特点的CTIA(电容互阻跨导放大器)作为列放大器读出结构,输出部分采用相关双采样(CDS)结构去除系统和背景噪声。实验结果表明,在3.5 nW的微光辐射下,器件偏压为-2.5 V时,50μm×50μm像素探测器与读出电路互联后有7.14×107V/W的电压响应率。     

Intrinsic Dynamic Properties of High-Characteristic Temperature GaInNAs Laser Diodes Operating at 1.3 μm

The properties of a high-characteristic temperature (T₀=155K) 1.3-mum GaInNAs-GaAs laser are presented with an emphasis on laser dynamic characteristics evaluated by linewidth enhancement factor and relative intensity noise. It is found that the relatively high differential gain of GaInNAs-GaAs quantum wells leads to a small linewidth enhancement factor of 2.8, indicating a small magnitude of frequency modulation with modulation current. The relative intensity noise measurements indicate a relaxation frequency of 4.7 GHz at a moderate bias current, from which the maximum intrinsic modulation bandwidth was calculated to be 9.7 GHz. The experimental determination of the low linewidth enhancement factor and high relaxation frequency reinforce the potential of dilute nitride lasers for high-speed directly modulated fiber links     

Modeling of the Transient Characteristics of Heterojunction Bipolar Transistor Lasers

A charge control model for the transient analysis of the bipolar transistor laser in forward active mode is developed to describe the dynamics of electron, photon and charge densities. From three coupled-rate equations, analytical expressions are obtained for the threshold base current density, the steady-state electron and photon densities, and small-signal frequency response. We find that the threshold current density decreases with increasing spontaneous emission lifetime of electrons in the quantum well as well as a linear dependence of the photon density on the base current. By optimizing the model parameters in their physical range, we show that a ${-}3$-dB bandwidth of 55 $~$GHz can be achieved for small-signal modulation of the laser. By numerically solving the rate equations, we investigate the ${-}3$-dB bandwidth under large-signal modulation to show that it remains nearly unchanged from the small-signal case. We further perform analysis of laser switching and find that the turn-on time is reduced by increasing the base current or decreasing the spontaneous emission lifetime of electrons in the quantum well.      

Giant linewidth enhancement factor and purely frequency modulated emission from quantum dot laser

Giant effective linewidth enhancement factors, close to 60, are measured on a quantum dot laser under specific biasing conditions. Consequently, 2.5 Gbit/s purely frequency modulated signal is obtained by direct current modulation at this operation point.     

注入锁定法布里-珀罗激光器的单模工作特性

使用分布式反馈(DFB)激光器对法布里-珀罗(F-P)激光器进行单模注入锁定.通过改变F-P激光器的偏置电流,DFB激光器的输出功率以及两激光器间的波长失谐量,对注入锁定F-P激光器的光谱特性、功率特性以及频率响应特性进行实验分析.找出影响注入锁定F-P激光器稳定性的因素,并测量注入锁定F-P激光器的稳定锁定区;通过优化注人条件实现F-P激光器的高边模抑制比(SMSR)输出,最高可达55 dB;通过与自由运转F-P激光器比较,发现注入锁定可以明显抑制半导体激光器在高频调制下光谱的展宽.注入锁定后F-P激光器的3 dB调制带宽接近14 GHz.实验结果表明,通过合理设计光注入条件,注入锁定技术可以明显改善F-P激光器的光谱特性以及高频响应特性,并在高速光纤通信领域中得到广泛应用.     

Steady-state and transient characteristics of microcavitysurface-emitting lasers with compressively strained quantum-well activeregions

In conventional semiconductor lasers, the dimensions of the optical cavity greatly exceed the photon wavelength, and the photon density of states forms a continuum since it is essentially that of a bulk system. On the other hand, in an ideal laser, one would like to have a single optical mode coincident with the maximum in the gain spectrum of the active medium. We show that substantial density-of-states quantization and enhancement of the fraction of photons spontaneously emitted into the lasing mode can be obtained by reducing the lateral width of the surface-emitting laser. For emission at λ=0.954 μm, the threshold current density can be drastically reduced by increasing the coupling factor to a few percent. For a cavity structure width of 0.3 μm, the threshold current density is 50 A/cm², compared with 250 A/cm² for the 0.6-μm cavity. At lower still lateral widths, the cavity loses its vertical character, and confinement of the lateral optical mode rapidly deteriorates. The large-signal response of microcavity lasers is slightly improved primarily due to elimination of mode competition in intrinsically single-mode microcavities, with relaxation times close to 1 ns. The enhancement of the spontaneous emission coupling factor results in an increase of the relaxation oscillation frequency and improvement in the standard small-signal response of microcavity lasers. For J=10J_th, the -3 dB modulation frequency exceeds 40 GHz. Since low threshold current densities may be achieved in microcavity lasers, the gains in small-signal performance are primarily extrinsic, i.e., higher modulation bandwidths ace accessible for the same injection