外部光反馈对强耦合外腔半导体激光器特性影响的理论分析

本文从理论上分析了外部光反馈对强耦合外腔半导体激光器特性的影响，对相干外部光反馈和非相干外部光反馈两种情形的分析结果均表明强耦合外腔半导体激光器可将半导体激光器所能容忍的临界光反馈强度提高大约２０ｄＢ以上，同时得出了长外腔和强耦合有利于提高外腔半导体激光器抗反馈能力的结论。     

光栅外腔半导体激光器的调谐范围

根据光栅反馈量的大小和近光栅端的半导体激光器端面反射率的变化，对光栅外腔半导体激光器的调谐范围进行了研究。     

光电反馈对半导体激光器相位噪声的改善

本文给出了光电反馈半导体激光器(LD)的相位噪声,指出:光电反馈可显著改善半导体激光器的相位噪声性能。     

光反馈对光纤光栅外腔半导体激光器特性的影响

主要研究了外加光反馈对光纤布拉格光栅外腔半导体窄线宽激光器特性的影响。在研究温度对光纤光栅外腔半导体激光器激射波长影响的基础上,设计了强度可调的外加光反馈系统,并利用延时自外差法测试外腔半导体激光器的线宽,从实验上分析了不同强度的外加光反馈对外腔半导体激光器线宽和噪声的影响。实验结果表明,在外加光反馈强度逐渐增强的过程中,激光器线宽逐渐变窄。当反馈比为-22dB时,激光器线宽被压窄至原始线宽的15%。与此同时,在相同的反馈变化下,激光器的相对强度噪声开始无明显变化,直到反馈比达到-27dB。再继续增大反馈强度,相对强度噪声显著增大,激光器内部发生相干崩塌。     

强反馈外腔半导体激光器线宽特性研究

本文分析了具有强反馈外腔的半导体激光器线宽特性，给出了强反馈外腔半导体激光器的线宽压窄率表示式．分析结果表明：该公式与数值解的结果符合很好，并且在一定条件下，弱反馈外腔可以得到比强反馈外腔更窄的线宽．     

强度反馈半导体激光器的量子噪声

本文提出了强度反馈半导体激光器的模型,分析了其量子噪声。分析表明:该半导体激光器的量子AM噪声性能优于普通半导体激光器的AM噪声性能。     

光纤光栅外腔反馈的高功率半导体激光器光谱特性的研究

对光纤光栅外腔反馈的高功率半导体激光器的光谱线宽特性进行了理论与实验研究。理论分析表明，根据不同的外腔参数，激光器的线宽能被压缩或展宽。外腔反射率对光谱线宽的影响要比外腔腔长灵敏得多。实验实现了激光器的线宽由６ｎｍ到０．８ｎｍ的压缩。光纤光栅外腔反馈不仅能改善高功率半导体激光器的光谱特性，而且可提高激光器主模对次模的抑制比。     

半导体激光器的原子法拉第反常色散光学滤波器光反馈稳频

为提高半导体激光器的频率稳定性，利用原子法拉第反常色散光学滤波器（FADOF）超窄带的选频透射特性，将其置于半导体激光器的外腔中作选频元件，采用光反馈的方法，使得透射率低的激光频率分量被抑制，透射率高的激光频率分量被加强，有效地实现了光反馈激光稳频。利用Cs原子法拉第反常色散光学滤波器工作于D2线852nm的4峰窄带透射状态。通过调节半导体激光器的温度和电流，调谐半导体激光器的输出波长，将激光器锁定在任何一个透射峰上，用26％的光反馈量，使稳频后的激光频率长期稳定性保持在75MHz／2h以内，而且采用这种稳频方法的输出激光中心波长一直稳定在频率基准上，没有单方向漂移。同时，还实现了Cs原子法拉第反常色散光学滤波器稳频半导体激光器结构的一体化，使其具有实用性。     

单量子阱半导体激光器在输出反馈损耗调制方式下的双稳特性

利用速率方程求出了输出反馈损耗调制型双稳半导体激光器输出光强稳态解的解析表达式。利用双区共腔ＧａＡｓ／ＡｌＧａＡｓ单量子阱半导体激光器，观测到半导体激光器在输出反馈损耗调制方式下的光双稳特性。比较速率方程解的理论计算曲线和实验观测到的双稳特性曲线后发现，两种双稳特性曲线随反馈损耗调制系数等器件参量变化的规律完全一致。     

具有强耦合外腔的半导体激光器稳定性极限条件

从理论上分析了强耦合外腔半导体激光器的稳定性。在外腔半导体激光器速率方程分析中引人了强反偏因子近似，通过增益速率－频率平面中的特性分析得到如下结论：对于给定参数的外腔半导体激光器，存在有一个技术不能超越的稳定性的理论极限条件。强反馈和短外腔长度有利于提高外腔半导体激器的稳定性．     

Transition from the lowest linewidth mode operation to coherencecollapse in a semiconductor laser with feedback from a distant reflector

The influences of optical feedback from a distant reflector on single-mode semiconductor laser operation are analyzed theoretically. The stable operation in the lowest linewidth mode and the feedback parameter for the onset of coherence collapse are systematically derived. In the feedback regime for the lowest linewidth mode operation, the laser principally operates at the emission frequency of the solitary laser at the beginning of the operation with the feedback. It is shown exactly by asymptotic analysis of the equation for the field phase in the semiconductor cavity considering the time-lag of the feedback that the laser comes to operate in the lowest linewidth mode. In the lowest linewidth mode operation, the laser is stably phase-locked to the feedback. In the semiconductor cavity, the field amplitude and the field phase oscillate in almost the same phase in the fluctuation modes related to the relaxation oscillations, In the lowest linewidth mode operation, the phase oscillations enhance the amplitude oscillations through the feedback-action's dependence upon the phase difference between the field in the semiconductor cavity and the feedback. Thus, the damping of the relaxation oscillations decreases with further increased feedback and the transition to the coherence collapse occurs     

Instability of coherence in semiconductor laser due to externalfeedback in hybrid-integrated optical waveguide components

The coherence instability of oscillation-frequency shift and spectrum-linewidth fluctuation of a distributed feedback (DFB) semiconductor laser due to reflected feedback from input or output facets in a butt-coupled waveguide device is theoretically analyzed. A low-loss butt-coupling method between a semiconductor laser and a waveguide device for hybrid-integrated optical components used in coherent optical-fiber systems is presented. The calculated results indicate that (1) the coherence instability of the DFB lasers is sensitive to external optical feedback, (2) feedback from the waveguide input facet affects the laser frequency and gain shifts, and (3) feedback from the output facet intensifies the linewidth fluctuations     

光通信源的相干检测

为了提高光通信系统的可靠性,利用光反馈半导体激光器在自由空间产生了通信源,实验中通过分析半导体激光器输出的相干特性,实现了对光通信源性能的检测。研究发现,无反馈时,激光器的输出为单模振荡,随反馈强度的增加,系统的输出经周期区域进入了混沌状态,通信光源的相干性逐渐变弱。此时系统处于复杂的随机变化状态,系统的抗破译能力强,利于隐藏信息,进行保密通信传输。     

半导体激光器电源中的反馈技术

本文讨论在半导体激光器电源中采用反馈技术来稳定激光器的驱动电流和输出光功率。     

Coherent optical interference effects in external-cavity semiconductor lasers

A broadening of the apparent linewidth of the semiconductor laser modes with external optical feedback is observed. This is shown to be due to the coherent nature of the feedback and multiple reflections in the external cavity. A theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed. The inclusion of these effects is also important in the interpretation of the threshold data of such lasers.     

Characteristics of chaos synchronization in semiconductor lasers subject to polarization-rotated optical feedback

We numerically investigate the detailed characteristics of chaos synchronization in semiconductor lasers subject to polarization-rotated optical feedback. The emission of the dominant TE mode of a drive laser is rotated 90 deg and fed back to the laser with time delay. The polarization-rotated TE mode is also injected with time delay into the TM mode of a second laser. Two types of synchronization with different time-lags are found, as in the case for synchronization in semiconductor lasers with nonrotated optical feedback. However, a significant difference to the nonrotated optical feedback case is that neither of the two types of synchronization requires matching of optical carrier frequency between the two lasers.     

Noise characteristics of a single-mode laser diode subject to strong optical feedback

An experimental study has been performed of the relative intensity noise (RIN) of a semiconductor laser in optical feedback regimes I to V. At low bias current, a low RIN is observed with low feedback ratio, the RIN increased in the coherence collapse regime (regime IV) and decreased in regime V. The RIN in regime V is lower than that of the solitary laser. For higher bias current, a higher feedback ratio is needed for the semiconductor laser to transit from regime IV to V. The measurements are found to be in good qualitative and quantitative agreement with theoretical predictions.     

AM noise enhancement in a semiconductor laser with electricalfeedback

A model of a self-heterodyne-type electrical feedback semiconductor laser is presented. The effects of electrical feedback on the AM noise of a semiconductor laser are discussed on the basis of the model. It is shown that the FM noise can be greatly reduced by electrical feedback. However, this reduction is always accompanied by AM noise enhancement. The AM noise can also be reduced by this scheme under some conditions with the enhancement of the FM noise. This means that AM noise reduction and FM noise reduction can be interchanged by using this method. The influence of feedback parameters on the noise is discussed     

DFB半导体激光器自注入锁定失稳因素分析

分布反馈(Distributed Feedback, DFB)半导体激光器具有体积小、成本低和工艺成熟等优势,但兆赫兹量级的线宽使其应用范围受限。采用环形谐振器对其进行自注入锁定,可将线宽压窄到千赫兹量级,但仍存在锁定不稳定的问题。文章采用四只不同的环形谐振器对DFB半导体激光器进行自注入锁定,通过实验监测自注入锁定时多个端口的光功率、偏振态和光波长的变化,揭示影响DFB半导体激光器自注入锁定稳定性的因素有谐振模式跳变、偏振态跳变,以及外界温度和振动引起的锁定环路的相位变化,且使用不同类型的环形谐振器进行锁定时,主导的影响因素不同。控制这些影响因素可以改善DFB半导体激光器自注入锁定的稳定性,使DFB半导体激光器自注入锁定技术有更好的应用效果。