高功率半导体激光器微通道热沉的方案设计

 对用于高功率半导体激光器的叠片式微通道热沉进行方案设计,利用计算流体力学和数值传热学对各种方案进行数值仿真,研究了微通道的特征尺寸和流量等因素对冷却效果和流动阻力特性的影响,一般情况下,减小微通道的特征尺寸和增加冷却水的流量可以降低传热热阻,但增加了流动压力损失;另外对金刚石热扩散片（次热沉）的效果也进行了数值计算,计算结果表明:金刚石热扩散片在该类型问题中降低温度作用明显。     

Thermal characterization of GaN heteroepitaxies using ultraviolet transient thermoreflectance

Thermal transport properties of GaN heteroepitaxial structures are of critical importance for the thermal management of high-power GaN electronic and optoelectronic devices. Ultraviolet(UV) lasers are employed to directly heat and sense the GaN epilayers in the transient thermoreflectance(TTR) measurement, obtaining important thermal transport properties in different GaN heterostructures, which include a diamond thin film heat spreader grown on GaN. The UV TTR technique enables rapid and non-contact thermal characterization for GaN wafers.     

Structural and phase characteristics of the diamond/matrix interfacial zone in high-resistant diamond composites

The structural-phase state of the contact zone and the factors that influence on the strength of diamond retention in the diamond carbide composites were determined. Composites were obtained by the new hybrid technology that eliminates the reheating of the metalized coating. The elaborated technology combines the thermal diffusion metallization of a diamond and the sintering by the scheme of self-dosed impregnation in a one-stage technological cycle. By the methods of electron microscopy, X-ray diffraction analysis, and Raman spectroscopy the structural and phase characteristics of the interphase boundary were investigated. The improvement of chemical and mechanical adhesion between the diamond and carbide matrix was obtained. It was shown that the specific productivity of the samples with a metalized diamond component is 39% higher than those without metallization.     

Mode locking a 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber

Passive mode locking of an optically pumped, InP-based, 1550 nm semiconductor disk laser by using a GaInNAs saturable absorber mirror is demonstrated. To reduce material heating and enable high-power operation, a 50 microm thick diamond heat spreader is bonded to the surface of the gain chip. The laser operates at a repetition frequency of 2.97 GHz and emits near-transform-limited 3.2 ps pulses with an average output power of 120 mW.     

High-peak-power optically pumped AlGaInAs eye-safe laser at 500-kHz repetition rate with an intracavity diamond heat spreader

We report on a compact efficient high-repetition-rate (>100?kHz) optically pumped AlGaInAs nanosecond eye-safe laser at 1525?nm. A?diamond heat spreader bonded to the gain chip is employed to improve the heat removal. At a pump power of 13.3?W, the average output power at a repetition rate 200?kHz is up to 3.12?W, corresponding to a peak output power of 560?W. At a repetition rate 500?kHz, the maximum average power and peak power are found to be 2.32?W and 170?W, respectively.     

High-power, (AlGaIn)(AsSb) semiconductor disk laser at 2.0 microm

We report a high-power (AlGaIn)(AsSb) semiconductor disk laser emitting around 2 microm. With a diamond heat spreader used for thermal management, a maximum output power of just over 5 W and slope efficiencies of over 25% were demonstrated. The output wavelength was tunable over an 80 nm range centered at 1.98 microm. The beam propagation parameter (M2) was measured to be in the range of 1.1 to 1.4 for output powers up to 3 W.     

10 W级主控振荡放大半导体激光芯片封装实验研究

结温升高是影响主控振荡放大(MOPA)半导体激光芯片输出功率的重要因素,为解决MOPA芯片的多电极封装和高效散热问题,提出了一种正装和热扩散辅助次热沉相结合的封装结构。建立了该封装结构的3D热模型,对比研究了倒装封装结构、正装无辅助次热沉结构与正装有辅助次热沉结构对MOPA半导体激光器结温的影响。计算结果表明,采用正装有辅助次热沉结构与倒装封装结构散热性能接近,且显著优于正装无辅助次热沉结构,结温降低幅度最高可达40%。另外,采用正装有辅助次热沉封装结构的MOPA半导体激光芯片在连续工作条件下输出功率为10.5 W,谱宽可实现半高全宽小于0.1 nm,中心波长随电流的变化约14 pm/A,实现了10 W级MOPA芯片的封装,验证了该封装结构的有效性。     

连续100W量子阱二极管激光器封装工艺

为了提高激光器输出功率,对研制的铜微通道冷却器性能进行了测试,分析了其散热能力。设计了一种在软焊料中掺杂金属添加剂的工艺,有效抑制了晶须生长,并利用该冷却器和新工艺封装出了连续100W大功率二极管激光器,并对封装的器件进行了性能测试。测试结果表明,封装的连续100W器件在工作电流105 A时,输出功率超过了100W,中心波长为808.5 nm,光谱半高宽为2.15 nm,器件的smile尺寸小于2μm,部分值小于0.5μm。     

新型交叉孔道式平板热管的性能研究

提出了一种设计交叉孔道式平板热管的新思路,按照这种方法设计加工的新型结构的平板热管均热器具有较强的轴向和径向导热能力,能明显减小导热热阻;特殊的孔道结构增强了毛细作用力,能有效强化相变换热。实验测试了不同热流密度和不同充液率下该热管正常工作时的稳态温度分布,给出了不同充液率和不同热流下的热阻,得到了热管的最佳充液率,证...     

Effect of heat spreader thickness and material on temperature distribution and stresses in thin disk laser crystals

Yb:YAG thin disk is mounted on the surface of the W–Cu heat spreader. The back side of the heat spreader is cooled directly using jet-impingement cooling system. In order to reduce the undesirable effects caused by the increase of temperature in gain medium, numerical analysis of the influence of material type and thickness of heat spreader was performed. The effect of various materials and thickness on temperature distribution, deformation and stress in disk laser is investigated using FEM analysis. Good agreement between the temperature distribution of numerical results and experimental thermography is obtained.     

Mounting-induced strains in red-emitting (Al)InGaP laser diodes tuned by pressure

The hydrostatic pressure behavior of red-emitting diode lasers packaged on Si, AlN, and diamond submounts is studied in the 0–2 GPa range by emission and photocurrent spectroscopy. Photocurrent spectroscopy allows for simultaneous measurement of the InGaP quantum well and (Al_0.5Ga_0.5)_0.5In_0.5P waveguide. A broadening of the absorption edge of the waveguide is observed for all devices and explained by the pressure-induced direct-to-indirect transition in this material. For the QW resonance, distinct differences are observed for differently packaged devices. Thus, very low pressure tuning rates are demonstrated for devices packaged on diamond and AlN submounts and explained by the presence of shear strain components. Consistently we find the device packaged on Si to be least affected by the strain caused by the pressure cycling.     

高密度封装二极管激光器阵列

 理论模拟了自制的高效冷却器的散热能力,分析了单元封装结构所需材料的导热特性,获得了高功率二极管激光器在高功率密度、高占空比条件下运行的可行性。改进了高密度封装的关键工艺,热沉金属化层达到了3~5 mm,焊料厚度为4~7 mm,封装间距0.6 mm,采用峰值功率1 kW的背冷式叠阵二极管激光器。实验测试结果表明:封装的二极管激光器叠阵单元的整体封装热阻为0.115 ℃/W,有良好的散热能力;该叠阵模块在电流为100 A、占空比15%时,输出峰值功率为986 W,峰值功率密度达到1.5 kW/cm2,平均每个板条的斜效率为1.25 W/A,激光器阈值电流为20 A左右。     

State equations and properties of various polymorphous modifications of silicon and germanium

The state equations and the pressure dependences of the lattice properties have been obtained for various polymorphous modifications of silicon and germanium using the Mie–Lennard-Jones pair interatomic potential and the Einstein crystal model. It is shown that the elastic-type interatomic potential gives the best results for the semiconductor phase and the plastic-type interatomic potential for the metalized phases whose potential well depth is significantly smaller. The pressure dependences of the lattice properties are calculated along isotherm 300 K and the jumps of the properties during the phase transition from the diamond structure to the β-Sn phase are evaluated for both silicon and germanium. The calculated results agree well with the experimental data.     

高功率二极管激光器封装的多层焊接技术

 对高功率二极管封装工艺中的焊接技术进行了研究，掌握了高真空下利用蒸发沉积制备铟（In）焊料的方法，在不加助焊剂的情况下进行了多层焊接实验，并对封装的连续、准连续激光器进行了性能检测。结果表明，利用In和In-Sn合金的多层焊接技术进行激光器封装的方法是切实可行的。     

Heat resistance of the interface in the silicon-on-diamond structure at a temperature of 80 K

Heat propagation at liquid nitrogen temperature in a heterostructure consisting of a polycrystalline diamond film deposited from hydrocarbon plasma on an oriented silicon substrate is studied. A technique for measuring the cooling kinetics of a thin-film indium thermometer deposited on a diamond film after heating by nanosecond pulses of a nitrogen laser is used. The experimental data are compared with the results calculated within the theory of heat conduction for multilayer systems. The analysis performedmade it possible to simultaneously determine the thermal conductivity of the diamond film and the interfacial heat resistance of diamond/Si and In/diamond interfaces at liquid nitrogen temperature.     

Solder with discontinuous melting point in semiconductor laser arrays and stacks

High power semiconductor laser arrays must be mounted in the epitaxy-side down configuration for good heat transfer and so require a well-controlled solder. Selection of solder is very important in semiconductor laser arrays and stacks. Usually, the solder consists of two layers. The outer layer prevents In from oxidation. A new type of solder with several layers of Au between the two layers of In was made, which constitutes of multi-layer of W/Ni/Au/In/Cu. In packaging, the Au layer in the solder does not melt. Quick temperature decrease can avoid expansion of the solder. The solder cannot oxidize during packaging.     

天然金刚石形成透明硼皮金刚石的研究

 本文采用离子注入法，对天然金刚石表面进行少量渗硼，形成透明硼皮金刚石。经NP-1型X光电子能谱仪（XPS）表面测试，证明注入硼后的金刚石表面硼原子和碳原子形成了结合键。又经热失重分析（TGA）表明，用B₂O₃和硼作离子源进行注入，均能使金刚石的抗氧化温度得到提高，但用硼注入得到的“硼皮”金刚石抗氧化性更好些。用四种不同能量进行注硼时，都能使金刚石的抗氧化性得到几乎相同程度的提高，与注入的深度无关。     

Thermal conductivity enhancement in Cu/diamond composites with surface-roughened diamonds

Cu/diamond composites have potential as a heat spreading material in small-scale devices. In this study, we show that the use of surface-roughened diamonds obtained by heat treatment under N₂ atmosphere and subsequently coated with a thin layer of Ti coating is a feasible method to effectively improve the interfacial bonding and thermal conductivity of Cu/diamond composites. The diamond surface state and prepared composites were investigated by the combination of X-ray diffraction, Raman spectroscopy and microstructure analysis. It is found that the surface-roughened diamonds are in favor of the formation of effective chemical bonds between diamonds and Ti coating through the formation of thin TiC layer and simultaneously provide increased Cu/diamond contact area, which are beneficial to largely decrease the interfacial thermal resistance and thus to greatly enhance the thermal conductivity of Cu/diamond composites.     

All-solid-state high-power conduction-cooled Nd:YLF rod laser

A high-average-power conduction-cooled diode-pumped Nd:YLF rod laser has been developed. A new conduction-cooled side-pumping scheme with a solid prismatic pump-light confinement cavity was employed. A transparent, high-thermal-conductivity MgF>(2) prism was used as a highly efficient pump cavity as well as a low-thermal-resistance heat spreader. The pumping efficiency and thermal resistance of the cavity were 85% and 0.20 degrees C degrees W, respectively. When this scheme was combined with heat pipes for heat removal, a maximum average output power of 72 W was demonstrated, with an optical slope efficiency as high as 49%.     

Discovery of a missing disease spreader

This study presents a method to discover an outbreak of an infectious disease in a region for which data are missing, but which is at work as a disease spreader. Node discovery for the spread of an infectious disease is defined as discriminating between the nodes which are neighboring to a missing disease spreader node, and the rest, given a dataset on the number of cases. The spread is described by stochastic differential equations. A perturbation theory quantifies the impact of the missing spreader on the moments of the number of cases. Statistical discriminators examine the mid-body or tail-ends of the probability density function, and search for the disturbance from the missing spreader. They are tested with computationally synthesized datasets, and applied to the SARS outbreak and flu pandemic.