C-mount封装激光器热特性分析与热沉结构优化研究

为了降低单管半导体激光器的结温、提高器件的散热效果,基于C-mount热沉的热特性分析提出了一种优化的台阶热沉结构,研究了单管激光器结温和腔面侧向温度分布曲线的影响。在热沉温度298 K和连续输出功率10 W的条件下,腔长为1.5 mm的典型C-mount封装结构激光器的结温为343.6 K,热阻为4.6 K/W。通过在典型C-mount热沉中引入台阶结构,使封装激光器的结温降低为333.8 K,热阻减小到3.5 K/W。计算表明,其输出功率可提高近20%。     

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。     

Thermal- and Spectral-Characteristics of High-Power Quasi-Continuous Wave 940-nm InGaAs Diode Laser Arrays

Experimental results of the thermal and spectral characteristics of a monolithic stack of high power quasicontinuous wave 940-nm InGaAs linear laser diode arrays have been evaluated. Thermal resistance as the most important thermal parameter characterizing a high-power laser diode package was obtained using the temperature rise measured directly by a thermo-camera. A new simple and convenient technique to measure a spectral transition of the emission from laser diode arrays is proposed. Spectral chirping due to the transient thermal power dissipated during the laser pulse was observed as a time-evolution of the spectral profile; it gave a comprehensible image of the chirping behavior. Comparing the temperature rise in the diode junction with the thermal simulation, it was determined that the thermal shift of central wavelength dλ/dT was 0.21 nm/°C. Detailed performances were identified for pumping a Yb³⁺ doped crystalline laser, and it was verified that the laser diode arrays were satisfactory to meet pumping source requirements for coupling to Yb³⁺ absorption linewidth.     

基于横向热流抑制的半导体激光芯片封装实验研究

为降低半导体激光芯片的慢轴远场发散角,提高其慢轴方向的光束质量,设计了横向热流抑制的封装结构。利用热沉间的物理隔离,削弱了半导体激光芯片慢轴方向上的温度梯度,有效降低了半导体激光芯片慢轴方向的发散角。采用热分析模拟了不同封装结构下芯片发光区的温度分布,并对波长915 nm的窄条宽半导体激光芯片进行封装。实验结果表明,在工作电流15 A,封装在隔离槽长4 mm,脊宽120 μm刻槽热沉上的芯片,其慢轴远场发散角由12.25°降低至10.49°,相应的光参量积（BPP）由5.344 mm·mrad 降低至4.5763 mm·mrad,慢轴方向亮度提升了约5.5%。实验结果表明,横向热流抑制的封装结构可以有效地削弱半导体激光芯片慢轴方向上由热透镜效应引起的高阶模激射,从而降低其慢轴远场发散角。     

环形激光二极管抽运棒状激光器中瞬态温度和热应力分析

直接从激光二极管发光强度的角分布出发,采用光线追迹方法获得激光棒内的热沉积分布,在此基础上采用热传导模型和热力模型,比较了不同抽运功率、不同棒半径下达到稳态温度分布的时间,并且对稳态和瞬态热应力进行了详细模拟计算。结果表明,采用环形激光二极管阵列侧面抽运的棒状激光器中的热效应问题十分严重,不同的抽运结构参量下,温度分布不同;达到稳态所需时间随棒半径增大而增加,而不受抽运功率的影响;抽运功率越大,棒内温差增大,热应力也越大;热破坏主要集中于激光棒中心区域和表面区域。     

大功率半导体激光器阵列热串扰行为

以硬焊料传导制冷,30%填充因子半导体激光器阵列为例,建立了三维有限元模型,对阵列内部各发光单元之间的热串扰行为进行了分析研究。结果表明,当其连续波工作时间大于1.2 ms后,阵列内发光单元之间出现热串扰现象;当次热沉由CuW合金改为铜金刚石复合材料时,阵列内发光单元自热阻和相邻发光单元的串扰热阻降低,有效地降低了各发光单元之间的热串扰行为。保持阵列宽度、发光单元数目及发光单元周期不变,发现随阵列填充因子的增加,器件热阻以指数衰减趋势逐渐降低,而发光单元间的热串扰特性对此变化并不敏感;保持阵列单个发光单元输出功率,发光单元尺寸及阵列宽度不变,增加发光单元个数后,阵列内各发光单元之间热串扰加剧,填充因子越高阵列升温速率越快;但在最初约70 s内,包含不同数目发光单元的阵列最高温度差异仅约0.5 ℃,有利于多发光单元高填充因子器件高功率输出。     

Three-dimensional time-dependent thermal model of catastrophic mirror damage in stripe-geometry double-heterostructure GaAs/(AlGa)As diode lasers

Three-dimensional thermal analysis of catastrophic mirror damage in stripe-geometry diode lasers was carried out in the present work. The spatial extent of the heat source at and near to the mirror surface as well as the temperature dependences of both the thermal conductivity and the thermal diffusivity are taken into account in the model. The heat conduction equation is solved by means of the Green function method.     

Semianalytical thermal analysis of rectangle Nd:GGG in heat capacity laser

Based on the theory of anisotropy semianalytical thermal analysis, the temperature field of rectangle Nd:GGG heat capacity laser crystal is investigated. Through an analysis of the working characteristics of the heat capacity laser crystal, a thermal model of heat capacity laser crystal is established. Using a new method for the anisotropic medium heat conduction equation, a temperature field expression of rectangle Nd:GGG heat capacity laser crystal for pumping stage and cooling stage is obtained, respectively. These results show that when using the output power of 300 W LD end-pumped rectangle Nd:GGG crystal for 10 seconds, the maximum temperature rise in the center of the pump face is 180.18°C, and after stopping pumping for 100 seconds, the maximum temperature rise drops to 0.74%. These results from this work provide a theoretical basis for the optimized design of a LD end-pumped heat capacity laser.     

Thermal Performance of Laser Diode Array under Constant Convective Heat Transfer Boundary Condition

Three-dimensional heat transfer model of laser diode array under constant convective heat transfer coefficient boundary condition is established and analytical temperature profiles within its heat sink are obtained by separation of variables. The influences on thermal resistance and maximum temperature variation among emitters from heat sink structure parameters and convective heat transfer coefficient are brought forward. The derived formula enables the thermal optimization of laser diode array.     

Dynamic thermal modeling and parameter identification for a monolithic laser diode module

We improved the thermal equivalent-circuit model of the laser diode module(LDM) to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.     

Dynamic thermal modeling and parameter identification for monolithic laser diode module

We improve the thermal equivalent-circuit model of the laser diode module (LDM) to evaluate its thermal dynamic property and calculate the junction temperature of the laser diode with a high accuracy. The thermal parameters and the transient junction temperature of LDM are modeled and obtained according to the temperature of the thermistor integrated in the module. Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines, and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.     

Simple formulae giving the temperature profiles in the stripe-geometry laser diodes with oxide barriers

Simple, approximate formulae describing the temperature distribution in the stripe-geometry laser diode with oxide barriers has been derived in this work. A two-dimensional, heat-spreading model has been used in which the lateral heat spreading as well as the radiative transfer of spontaneous radiation has been taken into account. The resultant formulae have been obtained using the electrical analogue of the heat flow process.     

Temperature dependent characteristics of InAs/GaAs quantum dot laser grown by gas source molecular beam epitaxy

We report on the temperature dependent lasing characteristics of InAs/GaAs quantum dot lasers under continuous wave mode. The five-stacked InAs quantum dots were grown by gas-source molecular beam epitaxy with slightly different thickness. Ridge waveguide laser with stripe width of 6 μm was processed on the growth structure. The characteristic temperature was measured as high as infinity in the temperature range of 80–180 k. With the increase of injection current, the lasing spectra of laser diode broaden gradually at low temperature of 80 k. However, when the operation temperature increases from 80 to 300 K, the width of lasing spectrum reduces gradually from 40 to 2.0 nm. The lasing process is obviously different from that of a reference quantum well laser which widens its width of lasing spectra by increasing operation temperature. These experiments demonstrate that a carrier transfer from the smaller size of dots into larger dots caused by thermal effect play an important role in the lasing characteristic of quantum dot lasers. In addition, the laser can operate at maximum temperature of 80 °C under continuous wave mode with a maximum output power of 52 mW from one facet at 20 °C. A wavelength thermal coefficient of 0.196 nm/K is obtained, which is 2.8 times lower than that of QW laser. The low wavelength thermal coefficient of quantum dot laser is mainly attributed to its broad gain profile and state filling effects.     

Jet-type, water-cooled heat sink that yields 255-W continuous-wave laser output at 808 nm from a 1-cm laser diode bar

A newly designed jet-type, water-cooled heat sink (the funryu heat sink, meaning fountain flow in Japanese) yielded 255-W cw laser output at 808 nm from a 1-cm bar made from InGaAsP/InGaP quantum-well active layers with a 67% fill factor [70 quantum-well laser diode (LD) array along the 1-cm bar]. A funryu heat sink measuring 1.1 mm in thickness gave the LD 0.25 degrees C/W thermal resistance, one of the lowest values achieved with a 1-cm LD bar. Over a short period of operation, the device reached a maximum cw power of 255 W. To the best of our knowledge, this is the highest power ever achieved in 808-nm LD operation. In the future, the funryu heat sink may be capable of 80-W cw operation over an extended lifetime of several thousand hours.     

基于沸腾-空化耦合效应的微通道线阵LD用热沉

 针对大功率LD的冷却需求,基于沸腾-空化耦合效应,研制了一种微通道相变热沉,封装腔长1.5 mm的LD线阵。依据加工条件确定通道宽度、深度以及间距,采用2维数值模型估算了通道长度,热沉材料采用无氧铜,多层叠焊,外形尺寸为20 mm×12 mm×1.6 mm。实验测试了连续功率LD输出0～100 W时的电 光转换效率以及电流 输出功率等特性,冷却工质采用R134a,磁驱齿轮泵电机转速50 r/s时热沉热阻为0.3 ℃/W。结果显示微通道相变热沉具有良好的散热能力,能够满足大功率LD的散热要求。     

激光二极管阵列泵浦固体激光器热设计研究

对激光二极管阵列（LaserDiodeArray,LDA）泵浦固体激光器热设计进行了研究。通过采用计算热阻的方法,根据LDA的发热功率选择热电制冷器（ThermaolElectronicConrtoller,TEC）和相应的散热器,采用强迫风冷的方式对重复频率为25Hz,输出单脉冲能量为80mJ的LDA泵浦固体激光器进行了精确的温度控制。试验结果表明,在-40℃～55℃环境温度范围内,激光器性能稳定,满足技术指标要求。     

Nonlinear distortion performance of narrow stripe-geometry lasers

Using the theoretical normalised current-light characteristic of a narrow stripe-geometry laser, an empirical formula is developed for the normalised light-current characteristic. Using this formula, closed-form expressions, in terms of the modified Bessel functions, are obtained for the nonlinear distortion components in the light resulting from exciting the laser diode by a multi-tone input current. These formulas can be used to predict the large signal performance of a narrow stripe-geometry laser diode by using simple hand calculations.     

采用半导体激光器自身pn结特性测温的 半导体激光器恒温控制

温度对半导体激光器的发射波长有很大的影响,而很多应用都要求半导体激光器的发射波长是稳定的。针对使用测温元件作为温度传感器进行半导体激光器恒温控制中存在的温度误差,提出了以半导体激光器自身pn结作为温度检测元件进行半导体激光器恒温控制的方法,设计了半导体制冷器的驱动电路。该方法利用pn结的温度敏感特性,首先通过实际测量标定pn结的温度与其两端压降的对应关系,然后通过测量压降得出相应的实际温度。实验结果表明,采用该方法消除了使用温度传感器进行半导体激光器恒温控制中温度梯度造成的恒温误差,提高了测量速度,显著减小了超调量,消除了静差和波动。     

Beam combining of a high-power laser diode bar on a temperature gradient heat sink

A new wavelength beam combining technique for a high-power laser diode bar by using a temperature gradient heat sink has been proposed. The thermal controlling principle of the temperature heat sink has been discussed. It has been proved by experiment that the linear temperature distribution, which generates linear wavelength spread of the output beams from a LD bar, can be obtained by introducing a temperature gradient heat sink and the output beams can be focused into a relative small spot by using the Czerny-Turner beam shaping system.     

Efficient pumping of Rb vapor by high-power volume Bragg diode laser

A 2W cw laser diode (LD) with an external cavity produced by a reflecting volume Bragg grating (VBG) demonstrated a spectral width of 7GHz (full width at half-maximum) at 780nm. The device output power exceeded 90% of the output power of the free-running LD. The emission wavelength was tuned over a 300pm range by thermal control of the VBG. Rb vapor was shown to absorb more than 95% of the laser radiation.