半导体激光器双波长光纤耦合模块的ZEMAX设计

为了发挥单管半导体激光器的优势,获得光纤耦合模块多波长、高功率、高亮度的光束输出,利用ZEMAX软件仿真模拟,设计了一种单管光纤耦合模块。此模块将32支输出波长分别为915 nm、975 nm,输出功率为15 W的单管半导体激光器,经过微透镜组快慢轴光束整形、空间合束、偏振合束、波长合束以及光束聚焦等一系列工艺后,耦合进芯径200 m、数值孔径0.22的光纤。模拟结果显示,光纤输出功率467.46 W,光纤前后耦合效率大于98.47%,总耦合效率高于97.39%,光功率密度高于12.86 MW/（cm2sr）,达到了泵浦激光器和功率型器件的性能要求。使用Solidworks软件设计了相应的底板结构,并结合ANSYS软件进行散热模拟分析,结果显示该模块散热性能良好,可行性较高。     

基于808nm半导体激光器单管合束技术的光纤耦合模块

由于单管半导体激光器比半导体激光线阵、叠阵具有更好的光束质量及散热特性,因此更适用于光电干扰光源。针对于电荷耦合器件(CCD)光谱响应曲线特征,采用808nm单管半导体激光器为光源,将24只单管半导体激光器分组集成,通过空间合束和偏振合束以提高其输出功率密度,采用自行设计的光学系统对光束进行扩束聚焦,耦合进芯径为300μm,数值孔径0.22的光纤中,所有激光器都采用串联方式,在8.5A电流下通过光纤输出功率为162W,耦合效率达到84%。     

高亮度半导体激光器泵浦光纤耦合模块

采用一种阶梯排列结构的单管激光器合束技术制成了高亮度半导体激光器光纤耦合模块,可用于泵浦掺Yb3+大模场双包层光纤激光器。利用微透镜组对各单管半导体激光器进行快慢轴准直,在快轴方向实现光束叠加,然后通过两组消球差设计的柱面透镜组分别对合成光束快慢轴方向进行聚焦,耦合进入光纤。实验中将6只输出功率为6 W 的976 nm单管半导体激光器输出光束耦合进芯径为105 m、数值孔径为0.15的光纤中,当工作电流为6.2 A 时,光纤输出功率达29.0 W,光纤耦合效率达到80.1%,亮度超过4.74 MW/cm2-str。     

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。     

半导体激光器边缘绝热封装改善慢轴光束质量

为了削弱激光器工作时芯片横向温度不均而导致的热透镜效应对慢轴发散角的影响,提高慢轴的光束质量,引入了边缘绝热封装方式,即在激光器芯片两侧与过渡热沉之间加入空气隙,以降低两侧的传导散热。利用有限元分析软件ANSYS 18.0对该封装结构中激光器芯片的温度进行仿真。结果表明:当工作电流为1.6 A,芯片与热沉的接触宽为200μm时,慢轴发散角由普通封装时的11.5°减小至8.2°,降幅为28%,光束参数积和光束质量因子也分别降低了28%和24%,热阻增大了6%。边缘绝热封装对器件激射波长、阈值电流、电光转换效率的影响很小。     

用于激光脱毛的低成本810 nm半导体激光模块

针对国内激光脱毛设备的需求,提出了宏通道加传导散热热沉的散热设计,并采用正交实验方法对影响宏通道散热能力的4个关键参数和3个水平进行了结构优化设计.仿真结果表明,对于该模块,本文设计的宏通道具有和微通道相同的散热能力.使用宏通道加传导散热热沉研制出低成本半导体激光器模块,测试结果表明,与设计值一致,输出峰值功率达到了603 W,波长807.5 nm,整体结构热阻为0.28℃/W,可以满足激光脱毛设备的使用要求.宏通道热沉成功取代了传统的微通道热沉,达到了降低成本的目的.     

窄线宽蓝光半导体激光器研究

由于有色金属对蓝光激光光源具有良好的吸收效率，因此蓝光半导体激光器逐步成为研究热点。针对激光加工纯铜、纯金、高强铝等高反射金属材料的市场需求，采用体布拉格光栅作为外腔反馈元件，压窄激光线宽，稳定激光波长，并基于空间合束技术将6片单管蓝光激光芯片聚焦耦合进芯径为105μm、数值孔径为0.22的光纤中，研制出窄线宽蓝光半导体激光光纤耦合模块。当工作电流为3 A时，该激光模块的输出功率为26.32 W，稳定输出波长为444.29 nm，光谱线宽被压至0.18 nm。     

大功率半导体激光器载体设计

激光器工作时由于存在各种非辐射复合损耗和自由载流子吸收等损耗机制,使注入到器件中的部分电功率转换成热耗散在激光器内,直接影响激光器的效率和寿命,因此散热处理一直是一个引人注意的焦点。采用微通道载体解决大功率半导体激光器阵列连续工作时散热问题,通过ANSYS软件模拟优化结构参数,实验测得了大功率半导体激光器阵列热阻。     

中红外半导体激光器合束技术研究进展(特邀)

中红外半导体激光器体积小、效率高,在环境检测、空间通讯及军事国防等领域具有重要的应用前景。但是中红外半导体激光器单元器件输出功率低,限制了其在以上领域的应用。激光合束技术是能够实现中红外半导体激光器功率提升的重要途径。文中详细介绍了几种用于中红外半导体激光器的合束方法及中红外半导体激光器合束方面的最新进展。     

高功率高亮度半导体激光器合束进展

半导体激光器体积小、效率高,但单元输出功率低、光束质量差限制了其应用。介绍了提升半导体激光器功率及光束质量的最新进展,对各种技术途径和实验结果进行了综述报道,并具体介绍了中国科学院长春光学精密机械与物理研究所近年来在高亮度半导体激光器芯片及合束方面取得的进展。     

Design of Bulk Thermoelectric Modules for Integrated Circuit Thermal Management

Various parameters affecting the performance of bulk thermoelectric (TE) modules used for integrated circuit (IC) thermal management are studied. An effective circuit model is developed that takes into account various ideal and nonideal effects in the module. It is shown that there is an optimum module thickness and an optimum operating current which depend on the overall heat dissipation and on the external thermal resistances. Optimized TE modules with ZT~0.8, will have a cross section over leg length ratio of 0.037m, can increase the chip operation power by 15% in comparison with the case without a TE cooler while maintaining the chip temperature below 100degC. This is for a package thermal resistance of 0.2K/W. Prospects for TE material with higher ZT values and the effect of contact resistance on the power dissipation density are also discussed. The results presented in this paper can be used in applications other than in the IC thermal management when external thermal resistances dominate the performance of TE modules     

Heat transfer from square pin-fin heat sinks using air impingement cooling

Experimental and numerical results are presented for heat transfer from a C4 mounted organic land grid array (OLGA) thermal test chip cooled by air impingement. Five heat sink geometries were investigated for Reynolds numbers ranging from 9,000 to 26,000. The dimensionless nozzle-to-heat sink vertical spacing z/D was varied between 2 and 12. In this study, we investigate the interactions between heat sink geometry, flow conditions and nozzle setting and how they affect the convective heat transfer and overall cooling of the test chip as measured by total thermal resistance /spl theta//sub ja/. Optimizing fin arrays by minimizing the overall heat sink thermal resistance instead of focusing solely on maximizing the heat transfer from the fins is shown to be a better design criterion. We also provide results that show cooling performance gains can be obtained by inserting a deflector plate above the heat sink.     

适用于大功率光电芯片散热的一体化平板热管

为解决大功率光电芯片散热问题,构造了一种新结构一体化平板热管。利用超轻多孔泡沫金属作为毛细吸液芯,以水、丙酮和乙醇为工质,在不同充液比、加热功率和倾角条件下对新结构热管的热性能进行了研究,结果表明,这种新结构平板热管不仅消除了热管与散热片间的接触热阻,而且使整个散热翅片也处于均温状态,当功率达到380W、热流密度超过445 W/cm2时,热管仍具有较好的均温特性,且热阻较小,可达0.04℃/W。在3种工质中,水是最佳工质选择,且当充液比为30%时具有较好的效果。实验表明,以泡沫金属为吸液芯的新结构一体化平板热管具有很好的传热性能,并扩展了承载大热流密度的能力。     

Development of liquid cooling techniques for flip chip ball grid array packages with High Heat flux dissipations

In this paper, development of single-phase liquid cooling techniques for flip chip ball grid array packages (FBGAs) with high flux heat dissipations is reported. Two thermal test chips with different footprints, 12 mm/spl times/ 12 mm and 10 mm /spl times/10 mm, respectively, were used for high heat flux characterizations. A liquid-cooled aluminum heat sink with an area of 15 mm (L) /spl times/12.2 mm (W) populated by microchannels was designed and fabricated. The microchannel heat sink was assembled onto the chip, using a thermal interface material to reduce the contact thermal resistance at the interface. A variable speed pump was used to provide the pressure head for the liquid cooling loop. The measured thermal resistance results ranged from 0.44 to 0.32/spl deg/C/W for the 12-mm chip case and from 0.59 to 0.44/spl deg/C/W for the 10-mm chip case, both under flowrates ranging from 1.67/spl times/10/sup -6/ m/sup 3//s to 1.67/spl times/10/sup -5/ m/sup 3//s. An analytical model of the flow and heat transfer in microchannel heat sinks is also presented. Computational predictions agree with the measurements for pressure drop within 15% and thermal resistances within 6%. The analytical results indicate that thermal interface resistance becomes a key limitation to maximizing heat removal rate from electronic packages.     

Double-sided cooling for high power IGBT modules using flip chiptechnology

A new technique for the packaging of IGBT modules has been developed. The components are sandwiched between two direct bond copper (DBC) substrates with aluminum nitride. Wire bonds are replaced with flip chip solder bumps, which allows cooling of components on both sides. Microchannel heat sinks are directly integrated in the package to decrease the thermal resistance of the module. Thus, a very compact module with high thermal performance is obtained. A prototype with two insulated gate bipolar transistors (IGBTs) and four diodes associated in parallel was realized and tested. In this paper, the innovative packaging technique is described, and results of thermal tests are presented     

Thermal characterization of a liquid cooled AlSiC base plate withintegral pin fins

In this study, we present the thermal analysis and experimental performance assessment of an aluminum silicon carbide (AlSiC) metal matrix composite (MMC) base plate with integral cooling fins. By attaching a pin-finned base plate to an open-chambered flow-through heat sink, the mechanical interface between the base plate and cooling medium is eliminated. This reduces the overall thermal resistance and improves module reliability as compared with traditional base plate cooling schemes. Computational fluid dynamics and heat transfer techniques were employed to model the thermal and hydrodynamic resistance characteristics through the pin fin structure of a prototype base plate design. A unit-cell approach was employed to avoid the computational expense of modeling the entire pin array. Performance was verified experimentally in a closed loop test facility using water as the cooling fluid. It was found that the unit-cell approach produced good agreement with experimental pressure drop and heat transfer results     

Modeling of TE cooling of pump lasers

The pump laser is a key module in optical amplifiers for long-haul fiber optic telecommunication systems. Its core component is a semiconductor laser diode mounted on a thermoelectric cooler. It is of crucial importance to maintain the laser diode temperature in a narrow range during operation in order to achieve satisfactory performance and reliability of the module. Therefore, a proper thermal management solution is very important to the pump module design. In this paper, a three-dimensional finite element analysis on thermoelectric cooling is presented. The modeling results show good agreement with the experimental results obtained by IR thermometry. When the heat source has a high power dissipation and a small footprint compared to the size of the heat sink, the spreading resistance becomes important. To analyze the maximum performance of the heat sink, both single and dual pump module configurations are considered.     

Encapsulated Thermoelectric Modules for Advanced Thermoelectric Systems

An encapsulated thermoelectric (TE) module consists of a vacuum-tight stainless-steel container in which an SiGe or BiTe TE module is encapsulated. This construction enables maximum performance and durability because: the thermal expansion mismatch between the hot and cold sides of the container can be accommodated by a sliding sheet in the container; the TE module inside is always kept in a vacuum environment, therefore no oxidation can occur; and the pressure difference between the inside and outside of the container reduces thermal contact resistance inside the container. Our encapsulated SiGe module features higher operating temperature—up to 650°C for both hot and cold sides. Other high-temperature modules and conventional BiTe modules, including both-sides and one-side skeleton types, have been encapsulated. Several variants of the encapsulated module are available. Encapsulated thermoelectric modules with integrated coolers contain cooling panels through which water can pass. If the module hot side is heated by a radiating heat source (radiation coupling) or convection of a hot gas or fluid (convection coupling), no pressing force on the module is necessary. It therefore features minimum contact resistance with the cooling duct, because no pressure is applied, maximum TE power, and minimum installation cost. Another, larger, variant is a quadruple flexible container in which four modules (each of maximum size 40 mm × 40 mm) are encapsulated. These encapsulated modules were used in a powder metallurgy furnace and were in use for more than 3000 h. Application to cryogenic temperatures simulating the liquid nitrogen gas vaporizer has been also attempted.     

Heat dissipation from silicon chips in a vertical plate,elevated pressure cold wall system

The heat dissipation effects of elevated pressure and cold gas temperature on vertically configured module mounted and free hanging chips were examined. It was found that with both types of chips, the thermal resistance (temperature rise x area/power) varies linearly with pressure in a log-log plot. A free hanging chip exhibits a (-1/3) power dependency on pressure while the module mounted chip exhibits a (-1/5) power dependency on pressure. The thermal resistance of the module mounted chip also appears to exhibit a dependency on gas temperature, but not on the difference in temperature between the chip and cold gas. The thermal resistance of the module mounted chip is some 5x lower than that of the free hanging chip, demonstrating that the module acts to a degree as a thermal expander. The efficiency is less than 20% based on the fact that the module area is some 30x greater than the chip area. For the module mounted chip, and a combination of a liquid nitrogen gas temperature and 1500 psi ambient atmosphere pressure, > 30 W/chip (0.180 in. × 0.180 in.) (0.46 cm × 0.46 cm), can be dissipated with a temperature rise to 85°C. This translates to a heat dissipation capability of more than 900 W/in².