窄线宽激光的零拍测量法

分析了用光纤延时零拍法测量窄线宽激光时 ,光纤延时线长度与零拍光电流谱线上的附加波动关系 ,利用该方法对有源光纤环形腔滤波器输出谱线进行了测量 ,其附加波动变化规律实验结果与理论分析一致。     

Thermal and Stark-Effect Roll-Over of Quantum-Cascade Lasers

A computational and experimental analysis of rollover in high-performance lambda ~ 8 mum quantum-cascade (QC) lasers is presented. In addition to conventional, thermal rollover, which is also a common cause of power rollover in diode lasers, ";Stark-effect"; rollover is observed. While both effects can occur in the same QC laser design, thermal and Stark-effect rollover are shown to be the dominating factor for high-temperature continuous wave operated, and pulsed low-temperature operated and low-doped lasers, respectively. Additionally, the role of the continuum above the wells and barriers is discussed for both effects.     

Thermal Behavior Investigation of Terahertz Quantum-Cascade Lasers

This paper investigates the heat conduction behavior of a terahertz (THz) quantum-cascade laser (QCL) active region by measuring its temperature using in-situ microprobe band-to-band photoluminescence (PL) technique. The heat resistance of different regions in QCL structure is derived from the temperature measurement. Experimental results show that thinning the substrate from 300 $mu{hbox {m}}$ thick to 140 $mu{hbox {m}}$ lowers thermal resistance of the device by 21%, which helps achieving continuous-wave operation. A thermodynamic differential equation was numerically solved and the temperature profiles and thermal behavior of various regions within actively biased QCL devices under various conditions were obtained. The simulation confirms the measured results that the substrate accounts for 59% of the total device thermal resistance.      

窄线宽半导体激光器的驱动和温控设计

窄线宽半导体激光器日益广泛的应用对其驱动和温控电路提出了更高的要求。为获得窄线宽、稳定功率并实时可调的激光输出,利用ATLWS200MA103驱动模块和TECA1系列温控模块搭建半导体激光器的驱动和温控电路,对激光器输出的各项性能指标进行测试,验证了在该驱动下,激光器线宽可达到5kHz,光功率稳定性达到0.1%。并利用波导谐振腔进行扫频实验,得出驱动电流变化量与激光器中心频率变化量之间的关系表达式。     

Thermal Modeling of Terahertz Quantum-Cascade Lasers: Comparison of Optical Waveguides

We compare a set of experimental lattice temperature profiles measured in a surface-emitting terahertz (THz) quantum-cascade laser (QCL) with the results of a 2-D anisotropic heat diffusion model. We evaluate the temperature dependence of the cross-plane thermal conductivity (kappa_perp) of the active region which is known to be strongly anisotropic due to its superlattice-like nature. Knowledge of kappa_perp and its temperature dependence is crucial in order to improve the temperature performance of THz QCLs and this has been used to investigate the longitudinal lattice temperature distribution of the active region and to compare the thermal properties of metal-metal and semi-insulating surface-plasmon THz optical waveguides using a 3-D anisotropic heat diffusion model.     

中红外量子级联激光器的研究进展

以不同结构类型的有源区为主线,如三阱垂直跃迁有源区、超晶格有源区、应变补偿量子阱有源区、束缚-连续跃迁有源区和四阱双声子共振有源区等,介绍了半导体能带工程在量子级联激光器中的应用。以不同技术指标和特性参数为主要内容,如激射波长、阈值电流密度、工作温度和输出功率等,评述了量子级联激光器在近3～5年内的研究进展。提出了进一步改善器件性能的可能途径,并指出了其今后研究的新方向。     

大能量窄线宽全固态钛宝石激光器的研究进展

主要介绍了用于差分吸收激光雷达系统和蓝绿激光通信的大能量、窄线宽全固态脉冲钛宝石（Tn：Al2O3）激光器的应用及其在国内外的研究历史和现状。阐述了目前获得大能量、窄线宽全固态钛宝石激光器的几种典型方法,比较了其优缺点,并对这种激光器的发展前景进行了展望。     

Heterostructures of Single-Wavelength and Dual-Wavelength Quantum-Cascade Lasers

The results of development of the basic structure and technological conditions of growing heterostructures for single- and dual-frequency quantum-cascade lasers are reported. The heterostructure for a dual-frequency quantum-cascade laser includes cascades emitting at wavelengths of 9.6 and 7.6 μm. On the basis of the suggested heterostructure, it is possible to develop a quantum-cascade laser operating at a difference frequency of 8 THz. The heterostructures for the quantum-cascade laser are grown using molecularbeam epitaxy. The methods of X-ray diffraction and emission electron microscopy are used to study the structural properties of the fabricated heterostructures. Good agreement between the specified and realized thicknesses of the epitaxial layers and a high uniformity of the chemical composition and thicknesses of the epitaxial layers over the area of the heterostructure is demonstrated. A stripe-structured quantum-cascade laser is fabricated; its generation at a wavelength of 9.6 μm is demonstrated.     

Linewidth in Widely Tunable Digital Supermode Distributed Bragg Reflector Lasers: Comparison Between Theory and Measurement

A transfer-matrix-based model is presented for calculating the linewidth of a widely tunable distributed Bragg reflector (DBR) laser as a function of its tuning currents. This model is used to calculate the linewidth of a digital supermode (DS)-DBR laser across its tuning range and compared to linewidth measurements under the same conditions. Excellent agreement is obtained with all the fine structure seen in the measurement being reproduced by the model. This suggests that the dominant factors which determine the complex structure of the linewidth are simple ones such as loss, threshold gain and optical power rather than complex details of the carrier dynamics     

半导体条形DH激光器中本征自脉动的精确理论

本文采用从实际电极等位体出发而不人为假设任何回定形式的注人电流分布的精确理论描述,进一步探讨了具有非自经波导的半导体条形D8激光瞩产生本征国脉动的物理机制及其内外因素的影响.指出偏置和外加电极电压上升时间对自脉动过程有巨大作用,并得出更愉确的自脉动区(出现自脉动的电压电流范回入     

5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality

Distributed Bragg reflector tapered lasers emitting at a wavelength of about 1060 nm were realized. The expitaxial layer structure leads to a vertical far-field angle of 15$^{circ}$ (full-width at half-maximum). The devices with a total length of 4 mm consist of 2-mm-long ridge waveguide and tapered sections. The input currents to both sections can be independently controlled. The laser reached 5-W output power with a narrow spectral linewidth below 40 pm (95% power) and a nearly diffraction-limited beam quality.      

Spectral Properties of THz Quantum-Cascade Lasers: Frequency Noise, Phase-Locking and Absolute Frequency Measurement

Quantum cascade lasers combine desirable features, namely high optical power and compactness, as no other coherent source in the field of THz generation. While their maximum operating temperature is progressively increasing, getting close to the range accessible by Peltier cooling, their range of application is expanding into new fields, such us molecular spectroscopy and their use as local oscillators. These applications would benefit from the investigation and improvement of the laser coherence properties. In this contribution we report the exploitation of electro-optic coherent detection based on a near-IR frequency comb to measure the frequency noise of a free running 2.5 THz quantum cascade laser. An intrinsic linewidth quantum limit of ~230 Hz has been measured, in good agreement with the Schawlow-Townes theoretical prediction. The same detection scheme is then exploited to phase-lock the quantum cascade laser line to a multiple of the comb tooth spacing, while a second comb allows to precisely measure the THz frequency. Such a dual frequency comb experimental setup thus yields a narrow line THz emission traceable to a microwave frequency standard.     

Effect of DBR Geometry on Reflectivity and Spectral Linewidth of DBR Lasers

对DBR几何参量不同的InGaAs-GaAs-AlGaAs DBR半导体激光器样品的输出线宽进行了测量和分析.样品激光器DBR光栅取不同的长度和蚀刻深度以考察其几何特性对耦合系数、反射率以及输出线宽的影响.线宽通过自差频测量系统测量得到.对实验结果与理论计算结果进行了对比.对测得的光学特性参数与几何特性参数之间的联系进行了分析.在此基础上讨论了DBR几何特性对激光器输出线宽的影响.研究结果为该类型DBR半导体激光器的制造提供了有用的信息.     

半导体激光器焊接的热分析

为了解决大功率半导体激光器的散热问题,利用有限元软件ANSYS,采用稳态热模拟方法,分析了半导体激光器内部的温度分布情况,对比分析了In、SnPb、AuSn几种不同焊料烧结激光器管芯对激光器热阻的影响。由模拟结果可见,焊料的厚度和热导率对激光器热阻影响很大,在保证浸润性和可靠性的前提下,应尽量减薄焊料厚度。另外,采用高导热率的热沉材料和减薄热沉厚度可有效降低激光器热阻。在这几种焊接方法中,采用In焊料Cu热沉焊接的激光器总热阻最小,是减小激光器热阻的最佳选择。通过光谱法测出了激光器热阻,验证了模拟结果,为优化激光器的封装设计提供了参考依据。     

调制掺杂压缩应变多量子阱激光器的增益特性和线宽增强因子的理论研究

本文首先从理论上分析并计算了压缩应变多量子陆激光器的增益特性，并且讨论了在多量子阱垒区进行Ｐ型强调制掺杂的情况下，价带空穴的准费米能级的移动以及微分增益谱的变化。     

自发发射因子在外腔半导体激光器的模式选择和线宽压缩过程中的作用

本文提出并论证外腔模式自发发射因子急剧减小使模式选择所需的增益差和光场相位噪声皆急剧减小是外腔半导体激光器具有优异的纵模选择和线宽压缩性能同时又具有严重不稳定性的统一的关键性物理根源。     

半导体激光器热特性测量技术的研究进展

分类讨论了半导体激光器热特性(温升)测量中所用的技术,介绍了各种技术的基本原理及其特点。     

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.     

半导体激光器封装中热应力和变形的分析

为了解决半导体激光器封装的热应力和变形问题,利用有限元软件ANSYS对SnPb、In、AuSn三种焊料焊接激光器管芯的情况分别进行了模拟,得到了相应的热应力大小和变形情况,分析了焊料和热沉对激光器热应力和变形的影响.对比了这几种不同封装方法的激光器发光区图像的弯曲程度,验证了模拟结果.由模拟和实验结果可见,采用In焊料是减小激光器热应力和变形的最佳选择.另外,适当增加热沉厚度,选择热匹配的材料,焊接时进行预热,可减小激光器的热应力和变形.通过模拟和实验分析,提出了减小热应力和变形的方法,为优化激光器的封装设计提供了参考依据.     

大功率半导体激光器阵列的稳态和瞬态热行为

大功率半导体激光器的应用日益广泛.随着激光器光功率的不断增加,其结温也在急速上升.激光器结温的升高不仪会导致寿命、斜率效率和功率下降,阈值电流增大,而且会引起波长漂移,光谱展宽等,因此开展半导体激光器热没计和热优化的研究显得越来越重要.用数值模拟和实验相结合的方法对单巴(bar)条CS封装的60 W,808 nm半导体激光器连续工作时的稳态和瞬态热行为进行分析研究,定量确定了半导体激光器的温升及其构成,以及器件的时间常数.此外,还对半导体激光器件做了热优化,并在分析结果的指导下做出了各项性能指标均优良的半导体激光器阵列器件.