Modulation properties of an injection-locked semiconductor laser

The modulation properties of an injection-locked semiconductor laser are investigated using the rate equation formalism. Intensity and phase modulations (IM and PM) are analyzed throughout the locking range where the locked laser is stable. The relaxation oscillation resonance in the IM and PM frequency responses can be dramatically reduced by tuning the injected power and the frequency difference between the master laser and the free-running slave laser. The power spectra under direct modulation are derived throughout the stable locking range. The spreading of the harmonics of the modulated locked laser is strongly affected by the frequency detuning, the injected power, and the injected current modulation. Measurements illustrating the theoretical results are also presented     

Coherent optical tapping using semiconductor optical amplifier

Semiconductor optical amplifiers are attractive not only as optical repeaters but also as functional devices, since carrier density modulation in amplifiers causes a nonlinear phenomenon. Utilizing the effect of the carrier density modulation on the semiconductor optical amplifier junction voltage, a coherent optical tapping is proposed for signal monitoring or control signal extraction. A 155 Mb/s FSK (frequency shift keying) signal tapping was realized with a simple configuration using heterodyne single-filter detection with -24.4 dBm sensitivity. Many applications for this coherent optical tapping are discussed, and basic characteristics for frequency-selective tapping from FDM (frequency division multiplexing) signals and optical amplifier gain control are examined     

Testing of high-power semiconductor laser bars

A measurement system called laser bar prober for characterizing high-power semiconductor edge-emitting laser bars is described. The laser bar prober is fully automated to handle testing of large numbers of lasers, is multifunctional to measure various laser characteristics and is accurate in predicting performance of fully mounted lasers. The bar prober has been proven to be an effective instrument for screening lasers during manufacturing process as well as an indispensable tool for providing rapid feedback to the development of new laser structures. In this paper, the design of the laser bar prober is described and a few examples of its applications are given; in particular, a time-resolved technique to correlate the measurement data of a laser within a laser bar to those of a fully mounted laser is demonstrated.     

大功率半导体激光器阵列

综合介绍了目前半导体大功率激光器普遍采用的材料结构、芯片结构、封装技术、散热致冷技术以及发展现状;给出了当前大功率半导体激光器的研究发展方向。     

大功率半导体激光器的可靠性研究

文中介绍了半导体激光器寿命测试的理论依据,给出寿命测试的数学模型,据此对InGaAsP/GaAs有源区无铝的808nm大功率半导体激光器进行高温恒流加速老化实验,得到器件在高温下的寿命,利用外推公式推算出激光器在室温条件下工作的寿命可超过30000小时。讨论了实验中出现的灾变退化,提出了防止灾变退化的几种方法。     

Coherent optical pumping of semiconductor lasers

The influence of coherent optical pumping in semiconductor lasers is investigated theoretically. In particular the mathematical conditions under which an optically pumped system behaves like an electrically (incoherently) pumped system are derived. We show that it is practically impossible to reach the interesting regime where coherent effects are important because of the inherent constraints to absorb photons at the pump frequency and to reach threshold gain at the lasing frequency. The effects of changing the temperature and of reduced dimensionality are discussed     

Submillimeter wave generation through optical four-wave mixingusing injection-locked semiconductor lasers

This paper presents a comprehensive analysis of submillimeter wave generation through optical four-wave mixing (FWM) in an injection-locked semiconductor laser. The probe wave introduces pump-probe difference frequency amplitude modulation (AM) and phase modulation (PM) of the slave laser injection locked to the pump wave. The AM and PM indexes of the locked laser output lightwave modulated at the submillimeter wave frequency have been calculated. The submillimeter wave power generated through this technique has also been calculated theoretically. The analysis predicts a submillimeter wave power of -3.7 dBm at 300-GHz frequency for a free-running slave laser output power of 30 mW. In the presence of amplitude modulation of the probe wave, the same modulation is transferred to the submillimeter wave. The suppression of output lightwave amplitude noise relative to the pump, probe, or free-running slave laser amplitude noise has also been estimated in this analysis. At a submillimeter wave frequency of 300 GHz and a probe power equal to the pump power, typical amplitude noise reduction occurs by 7 dB     

Locking bandwidth and relaxation oscillations of an injection-locked semiconductor laser

Detailed observations of an injection-locked semiconductor laser have allowed a verification of theoretical predictions for the locking bandwidth. In parallel, the fine structure of the intensity spectrum has been investigated and has revealed a strong modification of relaxation oscillation damping when locking is achieved.     

980 nm大功率高阶光栅锥形半导体激光器

为了获得高功率、窄线宽和近衍射极限输出的半导体激光器,采用高阶光栅（high order Bragg gratings,HOBGs）和主控振荡功率放大器（Master Oscillator Power-Amplifier,MOPA）结构,成功研制出一种980 nm波段的HOBGs-MOPA半导体激光器。该激光器采用周期为11.37 μm的高阶光栅进行光模式选择,通过锥角为6°的锥形波导将单模激光功率放大,实现了输出功率2.8 W,3 dB光谱线宽31 pm,光束质量因子M ²为2.51的窄线宽激光输出。     

圆环阵列多芯双包层激光相干合束的研究

由于受到纤芯面积、非线性效应等因素的限制,单芯光纤激光器的输出功率极限值为千瓦级.欲获得上百千瓦和兆瓦级的输出功率,必须借助合束技术.多芯双包层光纤激光相干合束法以其实验装置简单、自组织相干不需外界调制、泵浦光耦合效率高、纤芯阵列排列灵活等特点成为相干组束技术中一种比较有前途的方案.基于衍射理论推导出多芯双包层光纤激光器的远场相干光光强理论模型,在此基础之上,分析了纤芯数目、相邻纤芯轴间距离、纤芯直径、波长对合束的影响.分析结果表明:通过增加纤芯数目、减小纤芯间距离、在保证单模特性的前提下增大纤芯芯径可以有效提高合束效果.研究结果为优化相干合束方案、研制出高性能的多芯合束双包层光纤提供了参考.     

FM noise suppression and linewidth reduction in an injection-locked semiconductor laser

An expression is derived for the FM noise spectrum of an injection-locked semiconductor laser. For increasing injection level the FM noise spectrum and the lineshape change gradually from those of the slave laser to those of the master laser. The ultimate linewidth reduction is obtained if the locking bandwidth is large enough to accommodate the frequency fluctuations and if the detuning is controlled carefully.     

基于TEC的大功率LD恒温控制系统的研究

TEC存在功率有限、制冷效率低的问题,在用于大功率半导体激光器的温度控制时,常常无法达到所需的制冷效果.通过理论研究、软件仿真和实验验证,总结和提出了根据LD热负载选择TEC的理论依据和方法,以及与之匹配的大功率散热结构的设计优化准则.经实验验证,根据此原则设计的温控系统可在环境温度-40～55℃时,对30 W的LD实现恒温控制,温控范围20～40℃,温控精度0.5℃,实验结果表明此方法可以提高系统的整体效率,在设计大功率半导体激光器温控系统时具有一定的参考价值.     

Picosecond semiconductor laser radar with optical amplifier

An optical range finder, which uses the same semiconductor laser as both an optical pulse source and an optical preamplifier of the reflected pulse, is reported. This method has the advantage of reducing the number of optical components that must be aligned, which makes it suitable as a picosecond laser radar in aerospace applications. The device showed a maximum optical gain of 17 dB with a dynamic range of 33 dB, and the obtained resolution was of the order of 1 mm.     

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.     

基于半导体光放大器的可扩展型光开关矩阵

未来的高速和高度灵活的光分组交换网络要求开关速度达到纳秒量级且集成度高的大规模空间光开关矩阵。在分析了基于半导体光放大器的常用结构形式的光开关矩阵存在规模局限性的基础上,综述了新型的可实现大规模集成的基于半导体光放大器的光开关矩阵的基本原理和研究现状。     

Coherent homodyne optical communication receivers withphotorefractive optical beam combiners

The principles of operation and the results of performance measurements are reported of a new type of coherent optical receiver that used a dynamic volume index of refraction grating formed inside a photorefractive material to coherently combine signal and local oscillator light prior to photodetection. Because the refractive index grating is formed by the interference pattern generated where mutually coherent optical beams overlap, the receiver can automatically adjust to changes in angle of arrival or optical wavefront profiles which occur on time scales longer than the grating formation time. The grating appears stationary to high-speed phase modulation imposed on the signal beam and coherently diffracts local oscillator light into the signal beam direction. Performance measurements are reported for a prototype system that used two independent Nd:YAG lasers at 1.064 μm, an iron-doped indium phosphide photorefractive crystal, and a four-slot phase modulation signal format. A receiver BER of 10^-6 was obtained at received signal powers that corresponded to an average of 70 detected signal photons per bit at a source data rate of 50 Mb/s, 130 detected signal photons/bit at 220 Mb/s, and about 400 detected signal photons/bit at a 325 Mb/s source data rate. Quantum-limited operation corresponds to an average of six detected signal photons per transmitted information bit for this signal format     

大功率半导体激光器调制特性的实验研究

设计了一种带有调制输入接口及恒电流、恒功率、恒温控制的光源系统,着重对其低频调制特性进行了实验研究.通过引入负反馈及自动温度控制技术,从外部电路角度改善了半导体激光器的调制输出特性,有效抑制了驰豫振荡,优化了激光二极管(LD)的调制输出参数.     

External-cavity semiconductor laser tunable from 1.3 to 1.54 μmfor optical communication

Using semiconductor optical amplifiers with properly designed nonidentical quantum wells made of InGaAsP-InP materials in the external-cavity configuration, the semiconductor laser is broadly tunable. The tuning range covers from 1.3 μm to 1.54 μm. Without additional filtering techniques, the laser beam emitted from the linear external cavity has the sidemode suppression ratio better than 30 dB. Also, the power ratio of the lasing mode to the total output power is 90%-99%, indicating the dominance of the lasing mode in the amplification process due to the broad gain spectrum     

Coherent detection for optical duobinary communication systems

We propose and analyze coherent detection schemes for optical duobinary modulation. Thus, new quantum limits are established at 15, 30, and 31 photons/bit for coherent duobinary based on homodyne, heterodyne synchronous, and heterodyne asynchronous detection, respectively.     

腔面低反射大功率半导体激光器阵列

光束质量问题是制约半导体激光器应用的主要因素,采用出光面蒸镀低反膜LD阵列半导体激光器阵列锁相技术较好地解决了这个问题.本文设计并制作了高反膜系和极低反膜系,获得了高阈值的LD阵列.本文的低反膜系有大的带宽和小于0.2%的剩余反射率,易于工艺实现,LD阵列的阈值电流密度达到480A/cm2.