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.     

高功率Cr,Tm,Ho∶YAG激光器的实验研究

在医学应用上,Cr,Tm,Ho∶YAG激光器需要在大功率、高重频下工作。合理的设计对提高Cr,Tm,Ho∶YAG激光器的输出功率是很重要的。通过对Cr,Tm,Ho∶YAG输出特性进行理论分析和实验验证可知,腔长、全反射镜曲率半径、输出镜透过率、水温等因素对Cr,Tm,Ho∶YAG激光器的输出功率均有影响。提出了优化设计Cr,Tm,Ho∶YAG激光器的方法。在镀银腔情况下,当重频为10Hz时,激光阈值为45J,斜效率为1.1%;当输入能量为121J时,输出的平均功率为9.7W。在陶瓷聚光腔情况下,当重频为10Hz时,激光阈值为40J,斜效率为2.7%;当输入能量为100J时,输出的平均功率为16.2W。     

Efficient Tm:YLF laser with a volume Bragg grating recycle pumped by laser diode

By using a pump recycling configuration, we presented a high efficient diode-pumped Tm:YLF laser with a volume Bragg grating. When the incident pump power was 33.1 W, a maximum output power of 11.1 W at 1907.8 nm with full width at half maximum of 0.6 nm was obtained. The slope efficiency with respect to the incident pump power was 44.8%, and the optical-to-optical efficiency was 33.5%. In addition, the VBG-based Tm:YLF laser was employed as a pumping source of Ho:YAG laser, the maximum output power of 4.7 W with a slope efficiency of 67.0% was obtained, corresponding to Tm-to-Ho conversion efficiency of 51.6%.     

An Ho:YAG Laser with Double-Pass Pumping and the ZnGeP2 OPO Pumped by the Ho:YAG Laser

We report an efficient Ho:YAG laser end pumped by Tm:YLF lasers with double-pass pumping. We achieve the maximum continuous wave (CW) output power of 46.0 W with a single-pass pumping and 50.2 W with a double-pass pumping, corresponding to a slope efficiency of 58.0% and 62.8%, respectively. In addition, we use the Ho:YAG laser as a pumping source of the ZnGeP₃ optical parametric oscillator (OPO) and obtain the maximum average output power of 14.2 W with a linear cavity and 17.0 W with a ring resonator, respectively.     

LD泵浦掺铥(Tm3+)光纤激光器的数值分析

首先从掺铥光纤激光器的速率方程和光传输方程出发,建立数学模型,通过Matlab软件进行数值计算,分析了泵浦光和激光沿光纤的分布以及各能级离子数的变化.在不同掺杂浓度下,研究了小信号增益与入纤泵浦功率的关系以及泵浦光和激光功率与增益介质长度的关系.在不同泵浦功率下,研究了输出功率与输出耦合镜反射率的关系.进一步对不同泵浦吸收系数,研究了斜率效率和泵浦阈值与光纤长度的关系.分析结果表明存在最佳光纤长度和最佳耦合输出透过率,使得激光输出功率达到最佳值.     

角抽运Nd:YAG复合板条946 nm连续运转激光器

报道了一种适合中小功率输出的全固态激光器的角抽运方法, 抽运光从板条激光器中板条晶体的角部入射, 可获得较高的抽运效率和较好的抽运均匀性.采用单角抽运方式, 首次进行了角抽运Nd:YAG复合板条946 nm连续运转激光器的实验研究. 激光腔采用紧凑型平凹直腔结构, 腔长仅为20 mm. 当注入抽运功率为50 W时, 946 nm激光连续输出功率最高达5.29 W, 光光转换效率为10.6%, 斜效率为12%. 整台激光器结构紧凑, 调谐简单, 成本低, 具有广阔的应用前景. 关键词： 角抽运 Nd:YAG晶体 连续波 946 nm激光     

Ho:YAG laser intracavity pumped by a diode-pumped Tm:YLF laser

We report a compact Ho:YAG laser that is intracavity pumped by a diode-pumped Tm:YLF laser. Both lasers exhibit pulse mode behavior. Operating both crystals at room temperature (25 degrees C), we obtained 1.6 W of average output at 2.09 microm from the Ho:YAG laser for 15.4 W of diode power incident upon the Tm:YLF rod and a slope efficiency of 21%.     

A compact high efficient diode-double-passing-pumped mid-IR Tm:YLF laser at room temperature

A new compact high efficient diode-double-passing-pumped Tm:YLF laser at room temperature is presented. Using a crystal of 3 mm × 3 mm × 12 mm 4% doping Tm:YLF and double-end-double-passing pumping cavity structure without complex optical splitter pumping system, 5.6 W CW 1907.6 nm laser is obtained at 26.2 W 792 nm pumping laser. The slope efficiency is as high as 37.8% and the spectrum width is 2 nm. The relationship between cavity length and output laser is also analyzed. Experiments verify that the highest energy and convertion efficiency can be reached by optimizing the oscillator cavity length. Finally, we used this Tm:YLF laser to pump Ho:YAG crystal at room temperature and achieved 1.65 W 2.1 μm output laser with slope efficiency 67%.     

Tm3+:Ho3+共掺石英光纤激光器的实验研究

用铥钬共掺石英光纤,在钛宝石激光泵浦下,获得了波长为1870 nm、最大功率为240 mW的单模激光输出,斜率效率接近31％这是目前用该类光纤获得的最高转换效率研究了输出激光功率、输出光谱随泵浦功率、激活光纤长度的变化关系,并对相应结果进行了分析     

太阳光泵浦激光器侧面泵浦效率的提高

太阳光泵浦激光器直接利用太阳光作为泵浦源,实现了太阳光能量到激光能量的直接转化。设计了分腔水冷型金属锥形泵浦腔,以直径8mm,长115mm的Nd:YAG晶体棒作为激光工作物质,用有效面积1.03m2菲涅尔透镜会聚太阳光,实验获得了23.7 W的稳定激光输出,斜效率为7.87%。通过对比实验,改进后的分腔水冷型太阳光泵浦激光器较原有锥形腔激光器有55.92%的激光输出功率提升。分别从侧面泵浦光在冷却水中的吸收损耗以及其耦合效率等方面对新型腔体结构进行了分析,证实了分腔水冷型腔体结构对侧面泵浦效率的提高,并提出了陶瓷漫反射材质的分腔水冷型激光腔的设计。     

Pulsed and cw Cr,Tm:YAG laser with simultaneous diode and flashlamp excitation

A Cr,Tm:YAG laser, under simultaneous flashlamp and diode laser excitation, was demonstrated. With respect to diode pumping a cw-output power of 35 W with a slope efficiency of 20% was achieved. With flashlamp excitation pulse energies up to 465 mJ were realised. This operation was supported by simultaneous diode pumping to bring the laser close to threshold. Repetition rates up to 10 Hz were demonstrated with this simultaneous pumping mode of the Cr,Tm:YAG laser crystal.     

角抽运Yb:YAG激光器

报道了一种高功率准三能级激光器角抽运方法，抽运光从板条激光器结构中的板条工作介质的角注入，综合考虑抽运吸收、抽运亮度、晶体的掺杂浓度以及晶体尺寸等因素，进行了角抽运复合Yb:YAG激光器设计，实验上获得了最大连续输出功率400W, 斜效率28%的输出，实验结果充分证明了角抽运原理的正确性和应用于高功率激光器方面的可行性. 关键词： Yb:YAG 角抽运 复合晶体     

103 W in-band dual-end-pumped Ho:YAG laser

An efficient 2?μm in-band pumped Ho:YAG laser was demonstrated. The resonator involves two Ho:YAG crystals, each of which was dual-end-pumped by two orthogonally polarized diode-pumped Tm:YLF lasers. The maximum continuous wave output power of 103?W was achieved, corresponding to a slope efficiency of 67.8% with respect to the incident pump power and an optical-to-optical conversion efficiency of 63.5%. Under Q-switched mode, we obtained 101?W laser output at 30?kHz, corresponding to a slope efficiency of 66.2%. The beam quality or M² factor was found to be less than 2.     

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%.     

Highly efficient 2 μm Tm:YAG ceramic laser

We have experimentally demonstrated a highly efficient diode-pumped Tm:YAG ceramic laser operating at 2 μm wavelength. The maximum output power of 6.05 W was realized with a slope efficiency as high as 65%. As far as we know, it is the highest slope efficiency reported for Tm:YAG ceramic laser. The wavelength tuning experiment of Tm:YAG ceramic laser was carried out and the results suggest that Tm:YAG ceramic laser could operate simultaneously at multiple wavelengths in a wide range of 1884-2017 nm.     

激光二极管泵浦Nd：FAP激光器

报道激光二极管泵浦的掺钕氟磷酸钙固体激光器，该器件在重复频率为１００Ｈｚ的准连续状态下运行，当耦合输出透过率为８％时，得到３１％的斜效率，比较了ＦＡＰ和ＹＡＧ这两种介质的激光器的性能，理论分析得出的两者的阈值泵浦功率的相对值与实验结果相一致，并证实ＦＡＰ是一种有前途的适合激光二极管泵浦的激光介质。     

520-W continuous-wave diode corner-pumped composite Yb:YAG slab laser

We present a pumping scheme for a quasi-three-level solid-state laser. The scheme uses a slab laser configuration with the pump light incident from the slab corners. A diode-corner-pumped composite Yb:YAG-YAG slab laser operating in high-power cw mode was designed to prove the scheme. As much as 520 W of output power was obtained from a single 1-mm-thick composite slab with 0.5-at. %-doped Yb:YAG. The slope efficiency and the optical-to-optical efficiency with respect to the pump power were 32% and 25%, respectively. This result shows the validity of the corner-pumping concept and its feasibility in the development of high-power solid-state lasers.     

Comparison of Nd:YAG Ceramic Laser Pumped at 885nm and 808nm

Laser performance of 1064 nm domestic Nd：YAG ceramic lasers for 885 nm direct pumping and 808 nm traditional pumping are compared. Higher slope efficiency of 34% and maximum output power of 16.5 W are obtained for the 885nm pump with a 6ram length 1 at.% Nd：YAG ceramic. The advantages for 885nm direct pumping are discussed in detail. This pumping scheme for highly doping a Nd：YAG ceramic laser is considered as an available way to generate high power and good beam quality simultaneously.     

大功率准连续Nd:YAG陶瓷激光器研究

采用侧面环绕均匀排布的紧凑型抽运结构,实现了激光二极管阵列侧向抽运Nd∶YAG陶瓷激光器高效率激光输出。理论计算得到谐振腔输出镜的最佳输出耦合透射率为22.2%,并在输出耦合镜透射率为22%的条件下,用掺杂原子数分数为1%,尺寸为5mm×75mm的Nd∶YAG陶瓷棒,获得了平均功率大于230W的准连续1064nm激光输出,其光光效率和斜率效率分别高达52.4%和61%。并测得输出激光脉冲宽度为160μs,光谱线宽略小于0.8nm,光束发散角为16mrad。实验结果显示,Nd∶YAG陶瓷激光器输出功率Nd∶YAG单晶激光器相当。     

High-efficiency composite Tm:YAG laser

A high-efficiency continuous-wave Tm:YAG laser end-diode pumped at room temperature is presented in this letter. The highest output power reaches 6.37 W when the incident pump power is 18.9 W. The optical conversion efficiency is 33.7% and the slope efficiency is 42.8%. The wavelength of the output laser is shifted to the short wavelength with an increase in the transmission of the output couplers. At a fixed cavity length, the composite Tm:YAG shows its dominance for its higher efficiency and higher quantum efficiency compared with the noncomposite Tm:YAG.