1.5kW激光二极管抽运Nd∶YAG薄片激光器

报道了一台输出功率超过1.5kW的激光二极管抽运Nd∶YAG双薄片激光器。设计了四通光学耦合系统,通过优化经微柱透镜准直后光束的发散角,实现了抽运光的近平顶分布。薄片激光介质镀完介质膜后镀Ti,Pt,Au实现金属化,再采用铟焊工艺焊接在铜微通道冷却器上,以提高散热效率和冷却的均匀性。采用两片直径40mm,厚度1.3mm的Nd∶YAG薄片激光介质,在两个二极管激光器阵列抽运下,当每个薄片上的抽运峰值功率为17.7kW,占空比10%时,获得了平均功率1.52kW的准连续激光输出,光-光转换效率达到43%,电-光转换效率超过20%。     

1.5 kW激光二极管抽运Nd:YAG薄片激光器

报道了一台输出功率超过1.5 kW的激光二极管抽运Nd∶YAG双薄片激光器.设计了四通光学耦合系统,通过优化经微柱透镜准直后光束的发散角,实现了抽运光的近平顶分布.薄片激光介质镀完介质膜后镀Ti,Pt,Au实现金属化,再采用铟焊工艺焊接在铜微通道冷却器上,以提高散热效率和冷却的均匀性.采用两片直径40 mm,厚度1.3 mm的Nd∶YAG薄片激光介质,在两个二极管激光器阵列抽运下,当每个薄片上的抽运峰值功率为17.7 kW,占空比10%时,获得了平均功率1.52 kW的准连续激光输出,光-光转换效率达到43%,电-光转换效率超过20%.     

基于非均匀掺杂的激光二极管抽运固体激光系统放大介质热特性分析

利用非均匀掺杂的设计思想,针对正面抽运、背面冷却的有源反射镜放大器结构中不同激活离子掺杂分布的介质进行了模拟计算,分析并比较了传统均匀掺杂介质与非均匀掺杂放大介质中的温度、温度梯度、应力、应变以及波前畸变的分布。结果表明,与传统均匀掺杂介质相比,非均匀掺杂放大介质内的温度、温度梯度、应力、应变与波前畸变均有明显的降低。模拟结果证明,非均匀掺杂可以改善有源反射镜放大器构型冷却与产热异面的问题,可以有效地提高放大器增益介质热管理性能,为进一步讨论基于非均匀掺杂的放大介质的热管理优化提供了基础。     

千瓦级浸入式直接液冷Nd:YAG多薄片激光谐振腔

介绍了一种工作在准连续状态下的直接液体冷却的侧面抽运Nd:YAG多薄片激光谐振腔,装置中选用20片Nd:YAG薄片作为增益介质,由激光二极管阵列在其侧面进行抽运,流动的硅氧烷溶液作为冷却液在其端面进行冷却,振荡激光以布儒斯特角穿过多层薄片和冷却液实现增益。设计了层流冷却流场并通过数值模拟验证了其对来流不均匀性的耗散能力。根据之前报道的层流冷却能力测量实验建立数值模型,模拟了流场的冷却效果,实验结果证明了模型的置信性,进而基于模型对激光器中薄片的热安全性进行了评估。在抽运能量为49.9J时,获得了15.7J的最大脉冲能量输出,对应光-光效率和斜率效率分别为31.4%和39.2%;在抽运脉宽为250μs,重复频率为100Hz,平均抽运功率为5kW时,获得了1440 W的平均输出功率。     

梯度浓度掺杂复合板条抽运分布均匀性的分析

为了提高板条介质内抽运分布的均匀性,基于LD双端抽运Nd:YAG陶瓷板条放大器设计方案,理论分析了端面抽运条件下,单一浓度掺杂和梯度浓度掺杂板条介质吸收的抽运功率密度分布情况。通过分析可知,对于单一浓度掺杂板条,会产生抽运效率与抽运吸收功率均匀性之间的相互制约问题,而采用梯度浓度掺杂板条介质,在较高的抽收效率情况下,抽运吸收功率分布更加均匀。结果表明,采用梯度浓度掺杂结构可以提高板条介质内抽运分布的均匀性。     

激光二极管抽运Nd∶YAG双薄片激光器

激光介质的热效应是高平均功率固体激光器面临的最大挑战,采用薄片激光介质是解决热效应的有效手段之一。当在抽运区尺寸远大于薄片厚度并且抽运光均匀分布的条件下,热流近似为沿厚度方向的一维分布,从而大大降低介质的热透镜效应和热致应力双折射。设计了四通光学耦合系统,通过提高二极管激光器阵列输出激光强度分布的均匀性,并优化经微柱透镜准直后光束的发散角,实现了抽运光的近平顶分布。采用两片1 mm厚的Nd∶YAG薄片激光介质,在两个峰值功率2000 W,占空比为15%的二极管激光器阵列抽运下,获得了峰值功率1440 W,平均功率216 W的准连续激光输出,光光转换效率达到36%,电光转换效率超过16%,在稳腔下测得的光束质量M2因子约为12×13。     

激光二极管抽运Nd:YAG双薄片激光器

激光介质的热效应是高平均功率固体激光器面临的最大挑战,采用薄片激光介质是解决热效应的有效手段之一。当在抽运区尺寸远大于薄片厚度并且抽运光均匀分布的条件下,热流近似为沿厚度方向的一维分布,从而大大降低介质的热透镜效应和热致应力双折射。设计了四通光学耦合系统,通过提高二极管激光器阵列输出激光强度分布的均匀性,并优化经微柱透镜准直后光束的发散角,实现了抽运光的近平顶分布。采用两片1 mm厚的Nd∶YAG薄片激光介质,在两个峰值功率2000 W,占空比为15%的二极管激光器阵列抽运下,获得了峰值功率1440 W,平均功率216 W的准连续激光输出,光光转换效率达到36%,电光转换效率超过16%,在稳腔下测得的光束质量M2 因子约为12×13。     

二极管抽运Nd∶YAG薄片激光器研究

报道了采用脉冲二极管抽运的高功率薄片激光器。通过合理设计泵浦光四通薄片增益介质面泵浦耦合系统,实现了泵浦光在薄片增益介质的均匀泵浦;通过实验实现了1.2 kW的激光输出,光-光转换效率25%。     

LD侧面抽运的Nd∶YAG激光器抽运均匀性研究

通过对激光二极管 (LD)侧面抽运激光介质的分析研究 ,建立了二极管侧面抽运激光介质所吸收的抽运光功率分布的数学模型。采用光线追迹法模拟计算出单个二极管在不同抽运参数下直接抽运激光棒时 ,激光棒所吸收的抽运光功率的分布。比较了介质的吸收系数和二极管到激光棒距离的不同给抽运的均匀性带来的差异。计算了在有冷却系统的条件下 ,多个二极管阵列抽运时的抽运光功率分布 ,得到了较好的抽运均匀性     

基于空间载频干涉的薄片激光晶体热畸变测量

采用空间载频干涉方法在精确测量薄片激光晶体热畸变的基础上,深入研究了射流冲击冷却系统对薄片激光晶体热畸变的影响。实验结果表明,射流冲击冷却系统引起薄片激光晶体的畸变主要是球面形变。随着抽运功率的增加,薄片激光晶体的热畸变越发严重,在抽运区中心部分,以球面形变为主,其光焦度随抽运功率的增加呈线性下降。而在抽运区的边缘,以非球面形变为主,抽运功率越高,非球面畸变就越严重。给出了493 W抽运条件下热畸变的波前畸变曲线,其均方根的重复测量精度为1.153 nm。实验结果与理论分析结果相符,该研究为薄片固体激光器谐振腔的设计和热畸变的补偿提供了重要依据。     

用于板条激光器均匀面照明的三角形聚光器

用一个二维光线追迹程序,计算了三角形聚光器各几何参数对聚光效率及均匀性的影响,给出了适用于固体板条激光介质均匀面照明的结构参数。计算结果与实验基本一致。     

A high average power dual slab Nd:glass zigzag laser system

A dual slab Nd:LHG5 glass zigzag optical path laser was constructed with single-sided pumping and tested. A single slab (0.63 times 5.6 times 35cm) produced 80 W in an oscillator with an accompanying distortion of only 3 fringes (632.8 nm) as measured by a single-pass interferogram through the slab. Performance was achieved by producing uniform pumping and cooling of the slabs, and by controlling the distortion at the slab ends with pump shields.     

高功率固体激光系统棒状放大器的热畸变理论

建立了从棒状放大器能量沉积分布研究其热畸变理论的计算机模拟程序.可以计算棒状放大器泵浦期间和泵浦结束之后冷却过程中激光棒内的温度分布、应力分布、折射率分布以及激光束的退偏量、平均光束发散角和位相畸变.用哈特曼网格法测量了氙灯泵浦对激光波面的影响以及放大器的冷却过程.测量结果与计算结果一致.     

Uniform linear arrays of strained-layer InGaAs-AlGaAs quantum-wellridge-waveguide diode lasers fabricated by ECR-IBAE

Uniform linear arrays of strained-layer multiple-quantum-well InGaAs-AlGaAs ridge-waveguide diode lasers have been fabricated that operate near 980 nm and have low threshold currents I_th and high differential quantum efficiencies η_d. Uniformity was achieved by a combination of uniform ion-beam-assisted etching with an electron cyclotron resonance ion source and uniform organometallic vapor-phase epitaxial (OMVPE) growth. We investigated the effects of device geometry, namely, ridge width, cavity length, and remaining cladding thickness outside the ridge t, on I_th and η_d. For uncoated lasers with 500-μm-long cavities, 2- to 3-μm-wide ridges, and t=165±75 nm fabricated in double-quantum-well OMVPE material, I_th was typically in the range 6-7 mA and η_d was >40% per facet. A 24-element array of 2-μm-wide, 200-μm-long ridge-waveguide lasers with a high reflection coating on the back facet exhibited excellent uniformity, with threshold currents and single-ended differential quantum efficiencies that averaged 3.4 mA and 72%, respectively. Similar arrays with high-reflectivity coatings on both facets exhibited threshold currents as low as 2 mA     

Uniform distance and error probability properties of TCM schemes

The class of uniform trellis-coded modulation (TCM) techniques is defined, and simple explicit conditions for uniformity are derived. Uniformity is shown to depend on the metric properties of the two subconstellations resulting from the first step in set partitioning, as well as on the assignment of binary labels to channel symbols. The uniform distance property and uniform error property, which are both derived from uniformity but are not equivalent, are discussed. The derived concepts are extended to encompass transmission over a (not necessarily Gaussian) memoryless channel in which the metric used for detection may not be maximum likelihood. An appropriate distance measure is defined that generalizes the Euclidean distance. It is proved that uniformity of a TCM scheme can also be defined under this new distance. The results obtained are shown to hold for channels with phase offset or independent, amplitude-only fading. Examples are included to illustrate the applicability of the results     

Uniform wafer-bonded oxide-confined bottom-emitting 850-nm VCSELarrays on sapphire substrates

Uniform bottom-emitting 850-nm vertical-cavity surface-emitting laser (VCSEL) arrays on sapphire substrates have been demonstrated using wafer bonding technology to transfer the epitaxially-grown VCSEL structures from GaAs substrates onto sapphire substrates. The uniformity of the VCSEL arrays were improved by placing thin oxide aperture at the standing wave node to reduce scattering loss for small aperture devices. The averaged threshold current of a 5×5 VCSEL array is as low as 346 μA, while the averaged external quantum efficiency approaches 57%. The maximum wall-plug efficiency is 25% and the single-mode output power is more than 2 mW under continuous-wave current excitation at room temperature. We have also demonstrated a large (10×20) VCSEL array with variations of threshold current and external quantum efficiency less than 4% and 2%, respectively     

Uniform electron emission from a nitrogen-doped diamond-basedelectron emitter fabricated by the sintering technique

A nitrogen (N)-doped diamond-based electron emitter has been fabricated by the sintering technique prior to the chemical vapor deposition process in order to improve the uniformity. There are no spatial differences in reflective electron energy loss spectra (REELS) from the diamond-based electron emitter, suggesting that uniform surface conditions are obtained. The uniform electron emission from the obtained electron emitter is confirmed through emission current vs anode voltage characteristics measurements. It seems that the uniformity of the emitter surface results in uniform electron emission from the diamond electron emitter     

Reflector Design Method for Rotational Uniform Illuminance System with LED

Based on nonimaging design method, uniform illuminance systems with LED source were developed to create a uniform illuminated circular region with a desired size in a screen at a prescribed place. By using ray-tracing software based on Monte-Carlo method, the simulation results show that in the illuminated region the luminous uniformity is higher than 90%.     

均光波导多层存储器的原理和实验

介绍了均光波导多层存储器的基本结构和原理。波导多层存储器通过收集波导侧面信息符发出的散射光来读取数据,而均光波导多层存储器的设计主要是为了解决波导多层存储器侧面散射光强不均匀的问题。有一种方法就是通过改变信息符深度来实现均光。理论推导表明信息层表面的信息符深度沿着传导光传播方向逐渐增加时可以实现波导侧面散射光强的均匀分布,而且波导各个不同位置处信息符的深度值也可以通过拟合和计算得到。为了证明理论的正确性,设计了原理性实验,完成了原理性实验器件的研制。实验对均光波导多层存储器的结构、原理以及均光方法的可行性进行了验证。实验还将均光波导多层存储器的性能与一般的波导多层存储器作了对比,实验效果良好。     

Radiation Pattern Analysis of Uniform Rectangular Planar Arrays for Millimeter Wave Communications: Comparative Study with Uniform Linear Arrays

Radiation patterns of a Uniform Rectangular Planar Array deployed for millimeter wave communications are analyzed. Millimeter wave, as the name suggests, works on very high frequency bands i.e. 28, 38 and 72 GHz bands resulting in reduced antenna size. The size of these antennas are in the range of millimeters and therefore they are integrated on-chip. They can also be steered to achieve very high directivity and channel capacity. Directional antennas are implemented using beamsteering in millimeter wave communications to achieve very high data rates and also high capacity. The data rates are reported to increase by around 40 times as compared to off-chip or external antennas. In this paper, beam patterns for a uniform linear array and a uniform rectangular planar array with beamsteering are analyzed and compared.