半导体激光器的电噪声

通过测量激光器的电噪声,可以用来在线监测器件的诸多特性,如阈值电流的大小,是否有模式跳变发生,以及谱线宽窄等.另外,根据电噪声的大小,还可以对器件的质量和可靠性作出评价,具有快速、方便、无损等优点.文章概述了半导体激光器的电噪声,对其主要应用进行了综合和讨论,概括性评述了该领域目前的研究进展.     

半导体激光器混沌相位共轭反馈控制方法

提出了半导体激光器混沌相位共轭反馈(PCF)控制方法,建立了相位共轭反馈控制条件下激光器电流激发混沌的物理模型,发现其混沌控制物理机制是相位共轭反馈影响改变了激光器非线性增益和线宽增强因子特性,控制了系统的动力学行为及频率特性,其影响程度与反馈系数、延迟时间和光线宽增强因子等有关。数值模拟结果表明,在不同强度的光反馈下,通过调节相位共轭反馈光的延迟时间可以控制混沌激光到周期态、双周期态、多周期态等;发现相位共轭反馈控制特点是反馈光场和输出激光处于相干增强状态去实现混沌控制,且能控制实现激光器功率增强的周期脉冲输出。     

正反馈与负反馈

正反馈与负反馈的作用截然相反。凡促进化学反应者称正反馈,凡阻碍化学反应者称负反馈。举个具体例子,当被催化了的生产板浸入沉铜溶液时,板上的沉积反应发生了,这时被作用的对象又反过来作用于沉铜溶液。反作用的结果有两种:一种是化学反应被强化,称     

自差型光电反馈半导体激光器的量子AM和FM噪声谱

本文研究了自差型光电反馈(SHOE)半导体激光器(LD)的量子噪声,给出了AM与FM噪声谱的解析表达式,讨论了反馈环路参数的选择对量子噪声的影响。     

半导体激光器的噪声和带宽的测量

半导体激光器广泛地应用于光学测量、激光雷达、机载陀螺仪、信息处理、光通信、激光光谱和激光抽运原子频标等领域。在这些应用中半导体激光器的噪声和带宽是十分重要的参数,必须进行测量。本文详细地介绍了在激光抽运铷频标研制过程中激光器的噪声和带究的测试方法及实验结果。     

基于电反馈方法的窄线宽半导体激光器

窄线宽半导体激光器广泛应用于雷达和传感等领域,因此窄线宽激光器的研究具有十分重要的意义。设计采用了电反馈的结构,从激光器发射出来的光经过一个专门设计的频率鉴别器,来稳定激光器的中心波长。光电探测器将频率鉴别器发射出来的光转化成电流,与激光器内部探测器的电信号比较,比较之后的差值反馈到激光器将激光器的线宽锁定在环路带宽范围内;从而将激光器线宽由原始的0.5nm降低到0.08nm。     

Bistability in Semiconductor Lasers With Polarization-Rotated Frequency-Dependent Optical Feedback

Bistability in the emission frequency of a semiconductor laser subject to orthogonal-polarization optical feedback was recently observed experimentally by Farias in 2005, Phys. Rev. Lett. 94 173902 (2005). A frequency-sensitive filter (Cs-vapor cell) was placed in the way of the feedback beam to spectrally modulate the feedback power. Two different emission frequencies with the same output power were observed. This observation was understood in terms of a model that took into account the line shape of the filter and the empirical linear relation between the feedback-induced frequency shift and the feedback intensity. The model allowed to calculate steady states but not time-varying solutions. Here we present a rate-equation model that takes into account thermal and gain-saturation effects, and predicts a linear variation of the laser frequency with the feedback strength, together with a small power modulation. This model allows to study time-dependent solutions, and in particular, the transition between the two coexisting states. We show that numerical simulations using this model correctly reproduce the previous observed dynamics, and we present new experimental results in good agreement with our model for the laser response under orthogonal feedback     

Spectral Characteristics of Semiconductor Lasers with Optical Feedback

Optical feedback-induced changes in the output spectra of several GaAlAs lasers operating at 0.83 µm are described. The feedback radiation obtained from a mirror 60 cm away from the laser is controlled in intensity and phase. Spectral line narrowing or broadening is observed in each laser depending on the feedback conditions. Minimum linewidths observed with feedback are less than 100 kHz. Improved wavelength stability is also obtained with optical feedback resulting in 15 dB less phase noise. Analytical model for the three-mirror cavity is developed to explain these observations.     

Fundamental Thermal Noise in Distributed Feedback Fiber Lasers

A detailed analysis of fundamental thermal frequency noise in distributed feedback fiber lasers (DFB FL) is presented. An expression relating the laser frequency noise spectrum to the spectrum of thermal (temperature) fluctuations in the fiber, accounting for the nontrivial DFB FL mode shape, is derived. A new expression for the thermal fluctuation spectrum of single-mode optical fiber is derived which predicts high-frequency thermal noise 3 dB higher than previously published results. Theoretical predictions are compared against experimental measurements for a well characterized DFB FL. Anomalous 1/f noise at low frequency is discussed     

半导体激光器低频噪声测试及参数提取

半导体激光器低频电噪声的大小受器件潜在缺陷的影响,与器件可靠性具有相关性。介绍了半导体激光器噪声测试及参数提取的原理,设计了基于超低噪声前置放大器和低频频谱分析仪的低频电噪声测试系统,可测量半导体激光器的低频电噪声并提取相关噪声参数,进而通过低频电噪声的研究对半导体激光器进行可靠性评价,具有灵敏度高、非破坏性等优点。     

Dynamics of Broad-Area Semiconductor Lasers With Short Optical Feedback

The dynamics of filamentations in broad-area semiconductor lasers with short optical feedback were numerically studied. Regular pulse packages similar to those observed in narrow-stripe edge-emitting semiconductor lasers were found as the feedback reflectivity is increased. However, the regular pulse packages consisted of a periodic envelope of the external cavity frequency and fine pulse trains of periodic filaments, which is different from the regular pulse packages observed in narrow-stripe edge-emitting semiconductor lasers. From the analysis for spatio-temporal near-field patterns, we found periodic undulations of the spatial and temporal filament sizes as the external mirror reflectivity was changed. We also investigated filtered optical feedback, where a part of the emitted beam is fed back into the laser cavity. The time-averaged near-field pattern was found to have a strong dependence on the feedback level in the case of spatial filtered optical feedback.     

半导体激光器光输出噪声测量及与电噪声的相关性

采用互谱估计方法测量了半导体激光器的微弱电噪声谱及光噪声谱。结果表明两者在超辐射区有较强的相关性。对光噪声的形成机理分析证明由载流子起伏形成的光噪声与电噪声完全相关，而由外量子效率起伏引起的光噪声与电噪声是不相关的。     

Noise and Distortion Characteristics of Semiconductor Lasers in Optical Fiber Communication Systems

The distortion noise characteristics of semiconductor lasers in connection with optical fibers are reviewed. In particular, the intrinsic distortions, noise of semiconductor lasers together with the partition noise are discussed followed by a discussion on the influence of reflections. Modal noise phenomena due to the interference pattern at the endface of optical fibers are treated with respect to noise, distortions. Finally, the influence of polarization coupling in single-mode fibers on the resulting transmission behavior is discussed.     

半导体激光器动态量子AM和FM噪声的理论

本文用小信号分析的方法,研究了当对半导体激光器(LD)进行直接调制时(动态)LD的量子噪声,首次给出了LD的动态AM与FM噪声谱的解析表达式.分析表明,调制强度与调制频率均对LD的量子噪声有极大的影响.     

半导体激光器电噪声与非辐射复合电流的相关性

测量了50余只980 nm InGaAsP/InGaAs/AlGaAs双量子阱高功率半导体激光器的低频电噪声及其V-I特性。结果表明,小注入情况下,980 nm半导体激光器的低频电噪声主要表现为1/f特性,并与器件的表面非辐射复合电流有着良好的对应关系。     

半导体激光器电源与非辐射复合电流的相关性

测量了50余只980nmInGaAsP/InGaAs/AlGa As 双量子阱高功率半导体激光器的低频电噪声及其V－I特性。结果表明,小注入情况下,980nm半导体激光器的低频电噪声主要表现为1/f特性,并与器件的表面非辐射复合电流有着良好的对应关系。     

电反馈半导体激光器强度调制的最佳设计

本文研究了电反馈对半导体激光器强度调制的影响。在适当的反馈条件下,电反馈可以较好地改善半导体激光器强度调制的性能。并且存在着最佳反馈环路传递函数,使得其强度调制性能达到最佳。     

吸收光栅增益耦合DFB—LD电路模型

本文以激光器单模速率方程为基础,针对ＤＦＢ－ＬＤ推导了光子寿命与激光器内部损耗及端面出射损耗的关系,以及端面出射光功率与平均光子密度的关系,给出吸收光栅增益耦合ＤＦＢＬＤ电路模型,用该模型研究了ＡＧ－ＧＣ－ＤＦＢ－ＬＤ的自脉动效应及影响自脉动幅度和频率的主要因素。     

Experimental Investigation and Analytical Modeling of Excess Intensity Noise in Semiconductor Class-A Lasers

Excess intensity noise in a low-noise single-frequency class-A VECSEL is experimentally investigated over the frequency range 10 kHz-18 GHz. An analytical model is derived, based on multimode Langevin equations, to describe the observed laser excess noise over the whole bandwidth. From 50 MHz to 18 GHz, class-A operation leads to a shot noise limited relative intensity noise (RIN), namely -155 dB/Hz for 1-mA detected photocurrent, except at harmonics of the cavity free spectral range (FSR). At these frequencies, the excess noise is shown to be due to the amplified spontaneous emission contained in the nonlasing side modes. The measured levels of excess noise correspond to side mode suppression ratios (SMSRs) ranging from 70 to 90 dB, in agreement with the model. At low frequencies, 10 kHz-50 MHz, the observed excess noise spectrum has the expected Lorentzian shape. Its bandwidth increases with the pumping rate to an upper limit given by the cavity photon lifetime. Below this cutoff frequency, we show that the pump RIN is the dominant source of noise, while it is filtered by the laser dynamics above. Finally, our model permits to design a semiconductor class-A laser with an intensity noise limited to the shot noise level over the whole 10 kHz-18 GHz bandwidth.     

Phase Noise Reduction in FET Oscillators by Low-Frequency Loading and Feedback Circuitry Optimization

Optimization of low-frequency Ioading allows reduction of 1/f converted noise in FET oscillators. Moreover, an appropriate low-frequency feedback between drain and gate gives an improvement over previous results. This improvement is explained by taking into account the properties of the noise autocorrelation function.