Optically pumped potassium laser

We present an optically pumped continuous wave potassium vapor laser operating in a single longitudinal and a single transverse mode at 770 nm. The measured value of the input power to the output power slope efficiency was 20%.     

激光二极管端面抽运Nd:YVO4板条激光器及其热效应

激光器中激光介质采用板条状几何结构可以极大地降低它的热效应,但仍然需要进一步分析其影响,进而优化激光器效率.利用有限元分析方法分析了部分端面抽运的混合腔板条激光器中激光介质的热效应,计算的热透镜焦距与实测结果基本相符.分析了热效应对模式匹配的影响,分析结果对于优化激光器效率、改进谐振腔设计具有一定的参考价值.并在分析的基础上进行了混合腔实验,抽运功率为110 W时,获得连续输出激光功率41.5 W,光光转换效率约38%,斜效率达58.8%,M2因子为非稳腔方向M2x＝1.59,稳定腔方向M2y＝1.55.     

Efficient diode-pumped intracavity frequency-doubled CW Nd : YLF laser emitting in the red

We demonstrate an efficient continuous-wave diode-pumped Nd : YLF laser emitting in the red (660.5 and 657 nm) by intracavity frequency doubling with a LBO crystal. We obtained more than 1 W of average power (in two output beams) for 12 W of pump power with a TEM₀₀ mode. This power is to our knowledge the highest obtained with a frequency-doubled Nd : YLF laser emitting in the red. Comparison between “a-cut” and “c-cut” crystals has been carried out in terms of performance and wavelength emission.     

Blue laser light generation by intracavity frequency doubling of Cesium vapor laser

Blue laser light with a wavelength 447 nm was generated by intracavity frequency doubling of a Cs laser in PPKTP crystal. A continuous wave power of 600 mW was obtained at an optical-to-optical efficiency of 4%. In the pulsed operation, when thermal effects were reduced, the efficiency obtained was 14% and the peak blue power was 2.1 W.     

Generation of a uniform high-density microwave plasma for CO2 lasers using orthogonal electric fields

To realize a CO₂ laser using a fast-axial-flow high-output-power microwave discharge excitation, we devised a technology for making the microwave discharge uniform by varying the oscillation direction of an electric field with time. We also verified the effectiveness of this technology. As a result, we succeeded in increasing the discharge uniformity to 70% of the laser-tube cross-sectional area and realized a high laser output power and a high laser efficiency. In the case of a microwave input power of 1450 W, a maximum laser output power of 273 W and a laser efficiency of 18.8% were achieved; in the case of a microwave input power of 1070 W, a laser output power of 214 W and a laser efficiency of 20.0% were achieved. At the time of maximum output power, a high input power density of 280 W/cm³, which is approximately 20 times that in a dc discharge method, was achieved. Thus, a high-output-power microwave-discharge-excited CO₂ laser has become feasible. PACS 42.60.By; 52.80.Pi     

基于像散与理想光源成像原理的高亮度半导体激光器光纤耦合设计方法

运用像散原理和理想光源成像原理,讨论了半导体激光器消像散设计.提出了一种基于消像散的高亮度半导体激光器光纤耦合系统的设计方法.以波长为808 nm,输出功率为10 W的半导体激光器的光纤耦合为例,给出了详细的计算方法和设计步骤.结果表明:采用该方法将半导体激光器光束耦合入数值孔径为0.22,芯径为50 μm的光纤中,耦合后输出功率为9.712 W,耦合效率为97.12%,功率密度为1.1224×10⁶ W/cm².该方法不仅原理简单,而且设计的耦合系统耦合效率高、体积小,具有较强的实用价值.     

Diode-pumped passively mode-locked sub-picosecond Yb:LuAG ceramic laser

In this paper the laser activities of a diode-pumped Yb:LuAG ceramic which was prepared by the solid-state reactive sintering method were reported. The maximum output power was 1.86 W in the continuous wave(CW) laser operation,corresponding to a slope efficiency of 53.6%. The CW laser could be tuned from 1030 to 1096 nm by inserting a prism in the cavity. With the assist of a semiconductor saturable absorber mirror(SESAM), passive mode-locking was realized,delivering sub-picosecond pulses with 933 fs duration and an average power of 532 m W at a repetition rate of 90.35 MHz.     

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%.     

High power 1.3414 μm Nd:YAP cw laser

The eigen-oscillation mode of the Nd:YAP cw laser has been analysed. The influence of thermal effects arising from the pumping process on the output character of the 1.3414 μm Nd:YAP cw laser has been discussed. The crack problem of the reflective film at a 1.34 μm dielectric mirror has been solved. Based on the aforementioned work, we have been able to achieve an 82.8 W laser output at 1.3414 μm with a nearly polarized beam from a 5.8 mm diameter by 111 mm Nd:YAP rod. The overall efficiency and the slope efficiency are 1.15% and 2.02% respectively, and the fluctuation of the output power at 62 W is less than 1% during continuous operation for 45 min.     

Yb∶Y_2O_3陶瓷薄片激光器获得10.5 W连续激光输出

室温下采用中心波长约970 nm准直输出的大功率激光二极管模块作为抽运源,端面抽运双程吸收的腔型结构,抽运原子数分数为8%的Yb:Y2O3多晶透明陶瓷片获得连续激光输出。抽运阈值功率为7 W,当抽运功率达到35 W时,获得优化连续激光输出功率为10.5 W,光光转换效率为30%,斜率效率为37.5%。激光输出功率随抽运功率基本呈线性增长。采用更高功率抽运源、优化谐振腔结构和减小热效应的影响,Yb∶Y2O3陶瓷激光器的输出功率和效率将会得到进一步提高。     

1018nm光源及光纤激光同带抽运实验研究

设计了级联式全光纤1018nm光源。该光源采用两级级联放大方案,实现了对低功率1018nm种子光的放大,获得了4.2W的最大输出功率,并分析了影响放大效率的因素。以获得的1018nm激光为抽运源,进行了1070nm信号光的同带抽运放大器实验研究,测量了放大器的输出特性。在纤芯抽运实验中,获得了明显的放大效果和较高的功率转换效率。进行了瓦量级包层同带抽运的实验研究,分析了导致包层抽运实验中功率转换效率偏低的原因并提出了解决方案。     

A kilowatt level diode-side-pumped QCW Nd:YAG ceramic laser

We demonstrate a kilowatt level Quasi-continuous-wave (QCW) diode-side-pumped Nd:YAG ceramic laser at 1064 nm. The laser system adopts a master oscillator power amplifier scheme (MOPA). The master oscillator contains two diode-pumped laser modules. Under the pump power of 2000 W, an output power of 686 W was obtained. After amplified by an identical ceramic laser module, a maximum output power of 1020 W was obtained under a total incident pump power of 3433 W, corresponding to an optical-optical conversion efficiency of 29.7%. At the maximal output power, the repetition frequency was measured to be 1 kHz and the pulse width was 114 μs. To the best of our knowledge, this is the first time to realize QCW side-pumped Nd:YAG ceramic laser system with output power above 1 kW.     

High-power CW diode-side-pumped 1341 nm Nd:YAP laser

A high-power CW diode-side-pumped Nd:YAP laser with linearly polarization at 1341 nm has been described. The laser characteristics including thermal lens and stability of flat–flat resonator were studied. By comparing the output powers at different resonator lengths and different output couplers, the c-axis polarized laser working at 1341 nm has been obtained with a maximum output power of 121 W at the pumping power of 555 W. The optical–optical efficiency is 21.8% and the optical slope efficiency is 40%. The a-axis polarized laser at 1339 nm has also been successfully obtained when the c-axis polarized laser had become instable with the increase of pumping power.     

Growth and properties of KLu(WO4)2, and novel ytterbium and thulium lasers based on this monoclinic crystalline host

High‐quality crystals of monoclinic KLu(WO₄)₂, shortly KLuW, were grown with sizes sufficient for its characterization and substantial progress was achieved in the field of spectroscopy and laser operation with Yb³⁺‐ and Tm³⁺‐doping. We review the growth methodology for bulk KLuW and epitaxial layers, its structural, thermo‐mechanical, and optical properties, the Yb³⁺ and Tm³⁺ spectroscopy, and present laser results obtained in several operational regimes both with Ti:sapphire and direct diode laser pumping using InGaAs and AlGaAs diodes near 980 and 800 nm, respectively. The slope efficiencies with respect to the absorbed pump power achieved with continuous‐wave (CW) bulk and epitaxial Yb:KLuW lasers under Ti:sapphire laser pumping were ≈ 57 and ≈ 66%, respectively. Output powers as high as 3.28 W were obtained with diode pumping in a simple two‐mirror cavity where the slope efficiency with respect to the incident pump power reached ≈ 78%. Passively Q‐switched laser operation of bulk Yb:KLuW was realized with a Cr:YAG saturable absorber resulting in oscillation at ≈ 1031 nm with a repetition rate of 28 kHz and simultaneous Raman conversion to ≈ 1138 nm with maximum energies of 32.4 and 14.4 μJ, respectively. The corresponding pulse durations were 1.41 and 0.71 ns. Passive mode‐locking by a semiconductor saturable absorber mirror (SESAM) produced bandwidth‐limited pulses with duration of 81 fs (1046 nm, 95 MHz) and 114 fs (1030 nm, 101 MHz) for bulk and epitaxial Yb:KLuW lasers, respectively. Slope efficiency as high as 69% with respect to the absorbed power and an output power of 4 W at 1950 nm were achieved with a diode‐pumped Tm:KLuW laser. The slope efficiency reached with an epitaxial Tm:KLuW laser under Ti:sapphire laser pumping was 64 %. The tunability achieved with bulk and epitaxial Tm:KLuW lasers extended from 1800 to 1987 nm and from 1894 to 2039 nm, respectively.     

Tapered fused fiber bundle coupler capable of 1 kW laser combining and 300 W laser splitting

A high efficiency 7 × 1 multimode fiber coupler using the method of fusion and tapering is reported. This coupler can be applied to combine laser power, ad it can be used as a 1 × 7 splitter with reversible simultaneously. In the experiment, for combiner, coupling output power of 1032 W is obtained with the input power of 1066 W. The total coupling efficiency is 96.8%. The average insertion loss of each input fiber is 0.14 dB at ∼150 W input power. To splitter, the sum of 7 output ports power is 294 W with the input power of 341 W, and the insertion loss is about 13.8%. This fiber coupler can be applied in pumping all-fiber double clad fiber laser, as well as power combination and splitting of fiber lasers.     

Yb3+:Y2O3透明陶瓷激光器获得5 W连续激光输出

用带尾纤输出的激光二极管作为抽运源,采用端面抽运10％Yb^3 ：Y2O3多晶透明陶瓷的方式获得了连续激光输出。抽运阈值功率为5．6W,当陶瓷介质吸收的抽运功率为31．11W时,Yb^3 ：Y2O3多晶透明陶瓷获得了最大连续激光输出功率5．48W。光—光转换效率为17．6％,斜率效率为25％。同时在激光实验过程中,没有发现饱和现象,因此采用更高功率的激光二极管作为抽运源,陶瓷的激光输出功率会得到进一步提高。这一研究成果表明,多晶透明陶瓷是一种非常有潜力的激光增益介质。     

Characteristics of thermal distortions of the laser mirror substrates filled with phase-change materials

Under irradiating of the laser power of 2 kW, the thermal deformations of the silicon mirror substrates with phase change materials are experimentally measured and numerically analyzed by using finite element methods, respectively. The experimental results show that when the absorbed laser power is 120 W and the laser irradiating time gets to three seconds, the thermal distortion of the silicon mirror substrates with paraffin/carbon powder is 0.25 μm, that of the paraffin/aluminum powder 0.33 μm, and that of the paraffin/copper powder 0.37 μm. The numerical calculation coincides with the experimental results.     

Preparation and characterization of transparent Nd:YAG ceramics

Transparent Nd:YAG ceramics were produced by solid.state reaction of high.purity (4N) nanometric oxides powders, i.e., Al₂O₃, Y₂O₃ and Nd₂O₃. After sintering, mean grain sizes of 2% Nd:YAG samples were about 20 μm and their transparency were a bit worse than that of 0.9% Nd:YAG single crystal. Two types of active elements: rods and slabs were fabricated and characterized in several diode pumping schemes. In end pumping configuration as a pump source 20.W fiber coupled laser diode operating in low duty cycle regime (1 ms pump duration/20 Hz) was deployed. In the best case, 3.7 W of output power for 18 W of absorbed pump power, M² < 1.4 were demonstrated for uncoated ceramics Nd:YAG rod of ϕ 4×3mm size in preliminary experiments. For the ceramics of two times lower Nd dopant level above 30% slope efficiency was achieved. In case of Nd:YAG ceramic slab side pumped by 600.W laser diode stack above 12 W was demonstrated with slope efficiency of 3.5%.     

Industrial sealed-off copper vapor lasers with improved efficiency and radiation power

Results of experiments aimed at improving the efficiency and radiation power of industrial repetitively pulsed copper vapor lasers are presented. Design and technological improvements are described which increase the efficiency of a laser oscillator up to 1–1.2% relative to the input power drawn from a rectifier and up to 1.4–1.6% relative to the power fed into an active element. The possibility of improving efficiency up to 1.8 and 2.9% respectively is demonstrated. For a laser amplifier, the efficiency is 1.2–1.3 times higher than for an oscillator. For a laser oscillator and a laser amplifier, the power drawn from the active element is 37 and 44 W respectively for a working volume of 250 cm³, 44 and 60 W for a volume of 350 cm³, and 55 and 70 W for a volume of 900 cm³.     

基于光纤光栅的高功率光纤激光器

分析了光纤光栅的选频原理以及光纤光栅基高功率光纤激光器的阈值特性和输出特性.采用紫外写入的光纤光栅做谐振腔,研制了全光纤结构的高功率光纤激光器,泵浦阈值为186 mW, 最大输出功率1.78 W,斜率效率59%,实验结果与理论分析基本吻合.