大功率Nd∶YAG固体激光器

介绍了一台单级输出灯泵浦大功率脉冲Nd∶YAG激光器。该激光器脉宽0.1-10ms可调,频率1-1000hz可调,总注入电功率12kw。试验得到激光器参数脉冲宽度和频率协调改变,可使激光器在整个脉宽范围内都能稳定500w输出;最大单脉冲能量56J;总体电光效率4.2%;光束质量为25mm.mrad;功率稳定性±2%。     

大功率全固态激光数控加工机床

工业焊接切割使用的大功率激光器主要经历了CO．激光器、灯泵浦Nd：YAG固体激光器阶段,现在正向全固态激光器的应用方向发展。全固态激光器集半导体激光器和固体激光器的优势于一体,具有体积小、重量轻、效率高、性能稳定、可靠性好、寿命长、光束质量高等优点,近年来已成为激光学科的重点发展方向之一,大功率全固态激光器在工业加工、军事和科研等领域中有着十分重要的应用前景。     

基于LD双端面泵浦的Nd:YAG高效率倍频激光器

报道了一种利用激光二极管（LD）双端面泵浦的Nd：YAG激光晶体,Cr⁴⁺：YAG晶体被动调Q,LBO临界相位匹配腔内倍频的高转换效率的绿光激光器。分析了双端面泵浦YAG激光器的热效应,实验中LD双端面泵浦,采用U型平行平面腔结构对Nd：YAG进行传导冷却。当总泵浦光为33.8 W时,得到被动调Q频率10 KHz、功率8.21 W的线偏振基频光输出。6.72 W的绿光输出的倍频效率为86%,输出光束为基模,M²为1.4。实验表明双端面泵浦YAG倍频激光器具有很高的转换效率。     

激光二极管端面泵浦Yb:YAG圆棒热效应研究

基于激光二极管端面泵浦Yb∶YAG棒工作特点的分析,提出了端面绝热、周边恒温的激光晶体热分析模型,采用了一种新的热传导方程求解方法,得到了超高斯光束端面泵浦Yb∶YAG棒温度场的一般解析表达式。同时分析了不同阶次、不同光斑半径、不同功率超高斯光束以及晶体参数改变时对于Yb∶YAG棒温度场分布的影响。研究结果表明,若准直聚焦到Yb∶YAG棒泵浦面42.5W的光束具有4阶超高斯强度分布时,掺Yb3+质量分数为10.0at.%、长度为2.5mm、半径为2mm的Yb∶YAG棒的泵浦面获得74.20℃的最高温升。新的热传导方程求解方法在研究激光棒温度场分布方面具有计算量小、精度高等特点。研究结果对减小激光晶体的热效应,提高全固态Yb∶YAG激光器性能提供了理论依据。     

双掺Nd:Ce:YAG晶体激光输出特性

 为提高固体激光器的能量利用率,增大输出能量,将双掺Nd:Ce:YAG晶体的输出特性与普通Nd:YAG晶体进行了对比研究。分析了Nd³⁺和Ce³⁺的吸收光谱对激光晶体初始阈值反转粒子数的影响,结果显示:双掺Nd:Ce:YAG晶体可以提高晶体对泵浦光能量的利用率及激光器的输出能量,且可降低阈值泵浦能量。并分别检测了Nd:Ce:YAG激光晶体与Nd:YAG晶体的输出激光能量和阈值泵浦能量,实验结果表明：在输入电压为750 V时,Nd:Ce:YAG晶体与Nd:YAG晶体的输出能量分别为651.5 mJ 和390.4 mJ,能量利用率分别为2.31%和1.38%,激光振荡需要的泵浦能量阈值分别为10.56 mJ和15.21 mJ,且普通Nd:YAG晶体的斜效率为0.36%,而双掺Nd:Ce:YAG晶体的为0.49% 。     

种子注入的短脉冲激光器特性研究

 从LD泵浦固体激光器优化设计原则出发，设计了一种微型二极管泵浦激光器，并对种子激光器的结构和参数进行了优化。该激光器运转稳定，输出光束质量高，光束发散角小，光-光转化效率为17-4%，斜率效率可达24%，输出功率可达80mW。将此种子激光注入到调Q激光器中，改善了调Q激光器的输出特性，使得激光脉冲的建立时间缩短了40ns，输出的横模场分布得到了明显改善。     

直接水冷的Yb∶YAG薄片激光器系统设计与实验研究

设计了一台二极管泵浦的具有新型四通泵浦结构及接触式水冷装置的Yb∶YAG薄片激光器.激光泵浦源采用中心波长为940nm的二极管激光器,利用多模光纤进行耦合输出.YAG晶体Yb3+离子掺杂浓度为10%,几何尺寸为直径10mm,厚度500μm.激光晶体的散热装置采用自来水直接冷却,自来水通过铜热沉中打通的V型槽与薄片晶体直接接触.泵浦耦合系统采用聚焦透镜和一对直角棱镜的组合实现四通泵浦,聚焦透镜规格为直径50mm,焦距50mm.模拟了谐振腔的稳定性及不同腔长条件下所对应的激光光斑半径,设计了不同腔型的Yb∶YAG薄片激光器.在F-P腔中采用透过率为5%的输出耦合镜,获得了最高功率为3.28W的1 031nm连续激光输出,光束质量因子M2x=1.79,M2y=1.86,斜效率为20.5%.     

Cr~(2+):ZnSe全固态中红外激光器

建立了一种高质量、高效率全固态中红外激光系统,并对激光输出的效率、光束质量等指标进行了测试。首先,以二极管激光器为泵浦源,Tm~(3+):YAP晶体为增益介质,搭建了输出波长为1.97μm的近红外激光器。然后,以Tm~(3+):YAP激光器为泵浦源,自行开发研制的Cr~(2+):ZnSe单晶为增益介质,搭建了全固态中红外激光器。最后,测试了全固态中红外激光器的光束质量及激光器出光效率,并对谐振腔光效率的理论输出值与实际的激光器出光参数进行了对比。实验结果表明:此全固态中红外激光器的光光转换效率为17.2%,斜率效率为20%,在最高输出能量为3 W时的光束质量(M~2)在x和y方向分别为1.7和1.73,光束基本为圆形的高斯光斑。     

LD端面泵浦Cr~4∶YAG被动调Q激光器输出特性研究

对激光二极管端面泵浦Cr4+∶YAG被动调Q Nd∶YAG激光器输出特性进行了实验研究.实验研究发现,激光器输出功率及脉冲重复频率随谐振腔长度增大而增大.为解释这一实验现象,测量了泵浦光斑在激光晶体内尺寸,同时计算了激光晶体及Cr4+∶YAG晶体内的基模激光光斑半径随谐振腔长度变化.分析结果表明:激光晶体内泵浦光斑尺寸远小于激光晶体内基模光斑半径,腔模间交叠效率较低;当腔长增加时,激光晶体内的基模激光光斑减小,腔模间交叠效率增加,从而导致输出功率及脉冲重复频率随腔长增加而增加;另外,Cr4+∶YAG晶体内光斑半径也随谐振腔长度减小,引起Cr4+∶YAG晶体漂白时间缩短,导致脉冲重复频率随腔长增加而增加.     

高峰值功率KDP晶体四倍频266nm紫外激光器

报道了一种灯泵浦结构的Nd:YAG晶体电光调Q高峰值功率266nm紫外激光器。结合磷酸二氢钾(KDP)晶体性质,基于倍频理论,分析了考虑走离效应情况下存在相位失配量时KDP晶体长度对转换效率的影响。该激光器采用紧凑的平平腔结构,灯泵浦Nd:YAG晶体电光调Q 1064nm激光作为基频光,腔外采用Ⅱ类匹配磷酸钛氧钾(KTP)和Ⅰ类匹配KDP分别作为二倍频和四倍频晶体。利用能量计、示波器等仪器进行测量,激光器重复频率1Hz时,获得脉宽6.0ns,单脉冲能量35mJ的266nm紫外激光输出,峰值功率高达5.83 MW;当重复频率10Hz时,获得单脉冲能量28.9mJ的266nm紫外激光。532~266nm转换效率最高可达31.9%。利用该高峰值功率、窄脉宽266nm紫外激光器,能够实现激光打标、激光雕刻。     

600-W lamp pumped CW Nd:YAG laser

A lamp pumped CW Nd:YAG laser is presented in this paper for the requirement of industrial application. The main factors, which affect output power and beam quality of high power solid-state laser module, are theoretically analyzed. Total electro-optics efficiency of lamp pumped Nd:YAG crystal as high as 4.0% is obtained, and output power is higher than 647 W with beam parameter product 22 mm·mrad.     

Three-Rod Resonator for Krypton Lamp Pumped 1.8 kW Continuous-Wave Nd：YAG Laser

A three-rod series resonator cw Nd:YAG laser suitable for the industrial applications is presented. The symmetrical resonator laser has been developed and is rated at 1820-W output power with beam parameter product 24 mm.mrad. By utilizing the symmetrical resonator design, the characteristic of beam with multi-rod is not obviously decreased compared with that of a single one. The system total electro-optics efficiency of lamp pumped YAG crystal is as high as 4.0%. The main factors, which affect output power and beam quality of high power solid-state laser module, are theoretically analysed.     

四棒串接连续灯泵浦Nd:YAG大功率激光器

 报道了一种符合工业应用的四棒谐振腔连续Nd:YAG激光器。实验中采用对称放置方式四棒串接谐振腔得到2 105 W的平均功率输出，光束参数积24 mm·mrad，系统总光电转换效率达到3.5%。还对影响激光器工作的因素进行了理论分析。     

A highly efficient 5 kW peak power Nd:YAG laser with time-shared fiber optic beam delivery

Here, we report on the development of an efficient, high peak power lamp pumped Nd:YAG laser with time-shared fiber optic beam delivery. A maximum average output power of 270 W with 100 J maximum pulse energy and 5 kW peak power has been achieved with an electrical to laser conversion efficiency of 5.4%, which is on higher side for typical lamp pumped solid-state lasers. We have improved efficiency by spectral conversion and water flow optimization in the pump cavity, with a resulting beam quality comparable to commercial systems of similar power level. The resonator has been designed for stable operation from single-shot to 200 Hz repetition rate. A study of pulse-to-pulse laser energy stability for different resonator configurations has also been performed. The resonator was designed to achieve a good beam quality for the whole range of operation with a maximum beam parameter product of 15 mm mrad (M²45). A simple mechanism for time-shared fiber optic port selection has also been devised. Material processing applications such as cutting of stainless steel sheets up to 14 mm thickness and welding of metals such as carbon steel with weld depths up to 2 mm using the developed laser system has also been reported.     

7.3 W of single-frequency output power at 2.09 mum from an Ho:YAG monolithic nonplanar ring laser

Single-frequency output power of 7.3 W at 2.09 mum from a monolithic Ho:YAG nonplanar ring oscillator (NPRO) is demonstrated. Resonantly pumped by a Tm-doped fiber laser at 1.91 mum, the Ho:YAG NPRO produces 71% of slope efficiency with respect to absorbed pump power and nearly diffraction-limited output with a beam quality parameter of M(2) approximately 1.1.     

Two-pass amplification of CW laser by Nd/Cr:YAG ceramic Active mirror under lamp light pumping

The concept of an Active mirror with transparent Nd/Cr:YAG ceramics is proposed. A new ceramic material pumped by an arc-metal-halide lamp has been experimentally implemented. CW-laser light generated in a 1064 nm Nd:YAG micro-tip oscillator was amplified by an Active mirror made of Nd/Cr:YAG ceramic and pumped by CW arc-lamp light. The saturation power density of the Nd/Cr:YAG ceramic was lower than that of Nd:YAG because the stimulated-cross-section and lifetime were effectively enhanced by the sensitization of Cr ions. The maximum output laser power while keeping spatial beam quality was up to 3 W with an input lamp power of 9 W; the resulting optical-optical conversion efficiency of 33% was close to the theoretical prediction of nearly 50%.     

1064 nm Nd:YAG laser intracavity pumped at 946 nm

We present for the first time a Nd:YAG laser emitting at 1064 nm intracavity pumped by a 946 nm diode-pumped Nd:YAG laser. A 885 nm laser diode is used to pump the first Nd:YAG crystal emitting at 946 nm, and the second Nd:YAG laser emitting at 1064 nm intracavity pumped at 946 nm. We achieved an output power of 7.97 W at 1064 nm for an absorbed pump power at 946 nm of 9.55 W, corresponding to an optical efficiency of 83.4%. The beam quality M² quality factor is about 1.1 at the maximum output power.     

高功率高光束质量脉冲Nd: YAG激光器

 以实现高功率、高光束质量的脉冲激光输出为目的,对非对称平-凹谐振腔的结构进行了理论分析。设计出了高功率、高光束质量非对称放置的平-凹谐振腔、双氙灯泵浦的脉冲Nd: YAG激光器。当占空比为9%时,实现输出激光平均功率近480 W,光束参数积优于12.7 mm·mrad,电光转化效率近4%,与理论分析吻合,可用芯径300 μm的光纤传输,不稳定性优于±1%。加工实验证明有较好的质量：切割材料为不锈钢,厚度为3 mm时、切割速度为0.6 m/min和厚度为1.5 mm、切割速度为1.2 m/min时,两种情况下所得切缝宽度均为250 μm,且切割上下沿光滑。     

Characterization of laser processing of single‐crystal natural diamonds using micro‐Raman spectroscopic investigations

The application of lasers for processing diamond has revolutionized the diamond industry and its applications in microelectronics, microelectromechanical system (MEMS) and microoptoelectromechanical system (MOEMS) technologies. The process quality can be evaluated using spectroscopic techniques. In the present investigation, four different types of Q‐switched solid‐state lasers (with different beam parameters), namely, a lamp‐pumped Nd:YAG laser operating at 1064 nm, a lamp‐pumped Nd:YAG laser operating at second harmonically generated 532 nm, a diode‐pumped Nd:YVO₄ laser operating at 1064 nm and a diode‐pumped Nd:YAG laser operating at 1064 nm, have been employed for the processing of a single‐crystal, gem‐quality, natural diamond. The main objective behind the selection of these lasers with different beam parameters was to study the effect of wavelength, pulse width, pulse energy, peak power and beam quality factor (M² factor) on various aspects of processing (such as microcracking, material loss and cut surface quality) and their relative merits and demerits. The overall weight loss of the diamond and formation of microcracks during processing have been studied for the above four cases. The characteristics of the graphite formed during processing, elemental analysis, surface morphology of the cut surface and process dynamics have been studied using micro‐Raman spectroscopy and scanning electron microscopy (SEM). We observed that laser cutting of single‐crystal diamonds used for industrial applications can be accomplished without microcracking or surface distortion using Q‐switched Nd:YAG lasers. This allows direct processing without extensive postgrinding and polishing stages. Very efficient diamond processing is possible using diode‐pumped lasers, which results in the lowest possible breakage rate, good accuracy, good surface finish and low weight loss. From the micro‐Raman and SEM studies, it is concluded that the surface quality obtained is superior when diode‐pumped Nd:YVO₄ laser is used, owing to its extremely high peak power. The maximum graphite content is observed while processing with lamp‐pumped Nd:YAG laser at 532 nm. An overall comparison of all the laser sources leads to the conclusion that diode‐pumped Nd:YAG laser is a superior option for the efficient processing of natural diamond crystals. Copyright © 2006 John Wiley & Sons, Ltd.