Theory of spectral linewidth of external cavity semiconductor lasers

A new formula of the spectral linewidth of external cavity semiconductor lasers is proposed, with which linewidth narrowing with the optical feedback is discussed. It is shown that in the limit of large external cavity length, the linewidth caused by the phase diffusion due to spontaneously emitted photons becomes dominant and the linewidth decreases proportionally to the inverse of the external cavity length.     

Oscillation frequency shift suppression of semiconductor lasers coupled to external cavity

External cavity coupled semiconductor lasers are theoretically analysed for the suppression of oscillation frequency shift caused by current modulation and temperature change. The results indicate that strong optical feedback, AR-coating of laser facet and large ratio of passive/active cavity length are effective for the frequency shift suppression.     

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.     

Transient effects in external cavity semiconductor lasers

In several important applications of external cavity operated semiconductor lasers, including studies for FM optical communication and frequency stabilized lasers for coherent communication systems, the transient response of the laser is of crucial importance. In this letter, we present a first study of the transient optical response following a step current excitation applied to an AlGaAs laser operating in a dispersive external cavity. The study shows for the first time that, for optical feedback near the gain peak of the laser, a steady state is reached after only three roundtrips in the external cavity. However, for optical feedback far (∼100 Å) from the gain peak, 20 or more roundtrips are required before a steady state can be reached. It is also shown that under certain operation conditions the optical feedback can induce damped relaxation oscillations at each subsequent roundtrip in the external cavity.     

Intensity fluctuation in semiconductor lasers coupled to external cavity

Broad peaks are observed in the intensity noise spectrum for external cavity AlGaAs lasers. Oscillating longitudinal mode spectrum measured with a high resolution Fabry-Perot interferometer indicates that the intensity noise peaks result from the lasing of several closely spaced external cavity modes. A new mechanism is proposed to explain the observed noise spectrum; the intensity fluctuation is induced by modulation of the dielectric constant in the semiconductor cavity due to the beating of the electric fields for lasing modes. Qualitative agreements between the theory and experiments are obtained.     

Shaping current waveforms for direct modulation of semiconductor lasers

We demonstrate a technique for shaping current inputs for the direct modulation of a semiconductor laser for digital communication. The introduction of shaped current inputs allows for the suppression of relaxation oscillations and the avoidance of dynamical memory in the physical laser device, i.e., the output will not be influenced by previously communicated information. For the example of time-optimized bits, the possible performance enhancement for high data rate communications is shown numerically.     

自聚焦棒外腔单频半导体激光器

本文提出了用振幅耦合因子描述激光器谐振腔与自聚焦棒光波导结构的差异及耦合腔的衍射损耗;讨论了自聚焦棒相对激光器作微小偏移对振幅耦合因子的影响.对自聚焦棒外腔半导体激光器的选模理论进行了实验验证.实现了单纵模运转,其边模抑制比大于35dB,线宽小于21MHz,最大的波长调谐范围为11nm.     

解析式表示外腔半导体激光器的特征参量

用射线法研究了强反馈可调谐外腔式半导体激光器的阈值行为，导出了ＥＣＬＤ被财在不同波长振荡所需的阈值载流子数密度外腔长度及阈值电流的解析表达式，也得到了不同电流ＥＣＬＤ的调谐输出功率及载流子密度的表达式。     

Circuit models for frequency modulation response of semiconductor lasers

The authors describe a new circuit modelling technique for the directly frequency-modulated CSP semiconductor laser. In particular, this model accounts not only for the carrier density but also the temperature effects. Predictions from this model are compared with other published results of sinusoidal frequency modulation in the range DC-3 GHz and show good agreement.<>     

调谐外腔半导体激光器输出双稳环的确定

在考察了外腔半导体激光器(ECLD)的振荡频率ν与激光二极管(LD)中载流子密度N(或增益g)、介质的折射率n以及LD第m个模式的共振频率νm间的关系之后,利用微扰法对LD的N-ν曲线上被前人错判为不稳定的两个关键区段重新进行了分析,结果表明这两个区段是稳定区段,据此,可以确定在对ECLD进行调频的过程中其增益介质的N-ν曲线上出现的双稳环.     

半导体激光器外腔长连续调频特性的研究

研究了半导体激光器的外腔长连续调频特性，在外腔长λ／２变化范围内，激光频率与外腔长度呈线性变化关系，线性连续调频宽度小于外腔纵模频率间隔。外腔长调频率与激光管本征频率成正比，与外腔长度成反比。实验测量结果与理论分析相一致。     

Effect of external optical feedback on spectral properties of external cavity semiconductor lasers

The effects of external optical feedback on the spectral properties of single-mode external cavity semiconductor lasers that use a graded-index (GRIN) lens in the optical cavity have been investigated. Mode rejection ratio and intensity drop-out rate of the dominant mode as a function of optical strength have been measured. These measurements show that a laser with a short (160 ?m) GRIN-lens external cavity can tolerate optical feedback as large as ?20 dB without significant penalty. This minimum optical feedback can be larger when lasers with shorter cavity length are used.     

选频滤波器负载外腔半导体激光器调谐特性的研究

本文分析选频滤波器负载外腔半导体激光器的调谐特性。从等效模型的受激条件出发,导出确定最大调谐范围的简单表达式,提出了计算在各种反馈强度下调谐曲线的方法,并解释近年来报道的有关实验结果。     

光纤外腔对半导体激光器发光特性的影响

1.半导体激光器的张弛振荡、自脉动等光强起伏现象,以及用于光通信系统时,由光纤端面或光盘反射所引起的噪声对高速光通信的应用影响较大。为了抑制光强起伏,近年来外腔半导体激光器得到了较大发展。许多实验证明:外腔不仅能抑制张弛振荡和自脉动等光强起伏现象,而且还有很好的选模作用。甚至用外腔还做出了可调谐的单频激光器。这里,我们将一段光纤耦合到激光器上,利用光纤端面的反射形成光反馈作成了光纤外腔。 2.实验用的激光器是GaAlAs DH激光器,波长约为820nm,结构是质子轰击条形。用作耦合的光纤是标准的多模梯度光纤,芯径为50μm,数值孔径为0.2。激光器被烧焊在一个梯形的热沉上,其出光面直接与光纤耦合(见图1)。光纤的耦合端做成了球面,而另一端则做成平面,光反馈就是由此面反射形成的。光纤耦合端距激光器的距离约为50μm,     

外腔可调谐激光器调制特性研究

随着 WDM-PON(波分复用-无源光网络)应用中对低成本无色光发射模块需求的日益增长,基于混合集成的小型化外腔可调谐激光器,凭借其实现工艺简单、信号质量好和调谐范围宽等优良特性,受到越来越多的关注。文章在研究分析外腔激光器调制特性的影响因素的基础上,对特定结构的小型化外腔可调激光器进行了实验开发和特性研究,在激光谐振腔腔长对调制带宽的影响方面得到了一些有价值的结论,这可为后期器件开发提供理论支持。     

Theoretical analysis of longitudinal mode coupling in external cavity semiconductor lasers

The single longitudinal mode behavior in long external cavity semiconductor lasers is discussed. Experimentally, the laser exhibits a single frequency oscillation even for an external cavity length of 100 cm. The mode selectivity of a composite cavity is shown to be insufficient to explain the experiments. Longitudinal mode coupling in semiconductor lasers is found to arise from an interference effect between the modes on the interband transition probability of electrons. Mode coupling equations are derived, which indicates that the single mode oscillation in long external cavity semiconductor lasers is brought about when the coupling strength goes beyond a critical value. It is shown that the effect of the hole burning in the external cavity semiconductor lasers is similar to that in the solitary laser.     

外腔半导体激光器单频输出的长期稳定

一、引言 由于光纤通讯、光纤传感、检测二光谱分析、频标、光陀螺等领域的需要；单频半导体激光器的研究近年来受到广泛重视并得到迅速发展，由于采用了长外腔选模技术，已实现了线宽小于100 kHz的单频输出~[1-3]。而频率长期稳定工作则刚刚开始~[4]。通常认为，造成半导体激光器输出频率漂移及跳模的原因是管芯温度和注入电流的波动，因此稳频工作     

长外腔半导体激光器的调谐连续性

可调谐外腔半导体激光器（ＥＣＬＤ）中的波长选择元件（如光栅，Ｆ－Ｐ标准具等）所选择的波长函数具有一定的频谱宽度，为实现连续调谐该宽度就应足够小，作为首次尝试，在研究了确保ＥＣＬＤ能在激光二极管的以共振长振荡所需的条件后，我们导出该谱宽不能超过的上限值。     

光纤传感器用半导体激光器光频调制驱动电源

为了实现基于光频调制相位生成载波解调的干涉型光纤传感系统,需要对激光光源的频率进行调制.首先,文章根据直接电流调制原理设计井开发了一种半导体激光器光频调制驱动电源,主要由精密蕈准电压源、内部信号发生器,加法器、恒流源(电压电流转换、电流放大和电压负反馈)、慢启动电路、纹波抑制电路和过流保护电路等基本单元组成.接着,建立...     

Oscillation center frequency tuning, quantum FM noise, and direct frequency characteristics in external grating loaded semiconductor lasers

Simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented. Experimental results for the grating loaded AlGaAs lasers are in good agreement with the theoretical predictions. Remarkable reduction in spectral linewidth to less than 50 kHz is achieved by feeding back only 10^-3of the output power. Oscillation frequency stabilization, frequency jump behavior, and reduction in direct optical frequency modulation efficiency are also discussed.