Continuous-wave laser operation of Yb:LuVO4

We report on the room-temperature spectroscopic properties and continuous-wave laser operation of a new Yb:LuVO4 crystal. The peak absorption cross section for the pi-polarization is 8.42 x 10(-20) cm2 at 985 nm, and the stimulated emission cross section at 1020 nm is 1.03 x 10(-20) cm2. An output power of 0.36 W at 1041 nm was obtained with a slope efficiency of 47% by use of Ti:sapphire laser pumping. With diode pumping the output power reached 1.05 W at the highest available incident pump power of 6.8 W.     

An efficient continuous-wave YVO_4/Nd:YVO_4/YVO_4 self-Raman laser pumped by a wavelength-locked 878.9 nm laser diode

We report an efficient continuous-wave self-Raman laser at 1176 nm based on a 20-mm-long composite YVO_4/Nd:YVO_4/YVO_4 crystal and pumped by a wavelength-locked 878.9 nm diode laser.A maximum output power of 5.3 W is achieved at a pump power of 26 W,corresponding to an optical conversion efficiency of 20%and a slope efficiency of 21%.The Raman threshold for the diode pump power was only 0.92 W.The results reveal that in-band pumping by a wavelength-locked diode laser significantly enhances output power and efficiency of self-Raman lasers by virtue of improved pump absorption and relieved thermal loading.     

In-band pumped Er:YAG ceramic laser with 11 W of output power at 1645 nm

We report on a high power polycrystalline Er:YAG ceramic laser in-band pumped by a cladding-pumped Er, Yb fiber laser wavelength locked at 1532 nm with a volume Bragg grating. Using 1.0 at % Er³⁺-doped ceramic as the gain medium and an output coupler of 10% transmission, the laser had a threshold pump power of ∼1.5 W and generated 11 W of continuous-wave output at 1645 nm for 23.3 W of incident pump power at 1532 nm, corresponding to a slope efficiency with respect to incident pump power of 51%.     

Highly efficient Tm:YAG ceramic laser resonantly pumped at 1617 nm

We report on a highly efficient polycrystalline Tm:YAG ceramic laser in-band pumped by an Er:YAG laser at 1617 nm. Lasing characteristics of 4.0 and 6.0 at.%Tm(3+)-doped YAG ceramics were investigated and compared. With an output coupler of 10% transmission, a maximum output power of 7.3 W was obtained at 2015 nm under 12.8 W of incident pump power, corresponding to a slope efficiency with respect to incident pump power of 62.3%.     

双波长Yb∶YAG连续激光理论及实验研究

报道了Yb∶YAG双波长激光振荡阈值的理论结果,实验获得了连续双波长激光输出.实验中,采用紧凑的平凹腔结构、940nm光纤耦合LD端面泵浦方式,Yb∶YAG晶体作为激光晶体,采用10%、15%和20%的输出耦合镜,分别实现了单波长和双波长激光输出,在最高泵浦功率为20 W时,输出耦合率分别为10%、20%,最高获得3.94W的1 050nm激光和3.40 W的1 030nm激光,对应的光光转换效率分别为19.7%和17.0%;当输出耦合率为15%、泵浦功率为11.7 W时,获得0.79 W的双波长激光,对应的光光转换效率为6.8%,功率比为1∶1.3,通过光栅光谱仪测量得到双波长谱线中心分别为1 030.31nm和1 047.50nm;当1 030nm激光功率为3.0 W时,30min内输出功率RMS稳定性优于0.18%.该实验结果与理论分析相吻合,可应用于设计稳定可靠的掺Yb双波长激光器.     

Diode-end-pumped 4.2-W continuous-wave Yb:Y2O3 ceramic laser

We report on an efficient diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Continuous-wave output power of 4.2 W at 1078 nm was obtained under pump power of 19.5 W. The corresponding slope efficiency was 29%. The beam quality factor (M2) at full pump power was measured to be 1.63. The threshold wavelengths of the laser at various output couplings were also investigated. It was found that the threshold wavelengths shifted approximately 5 nm when the reflectivity of the output coupler changed from 90% to 99.9%, as caused by the strong reabsorption effect in the ceramic sample.     

Low-power-pumped high-efficiency frequency doubling at 397.5 nm in a ring cavity

We report low pump power high-efficiency frequency doubling of a fundamental laser beam at 795 nm, corresponding to the rubidium D1 line, to generate UV light at 397.5 nm using a periodically poled KTi OPO4（PPKTP） crystal in a ring cavity. We obtain maximum stable output power of 49 m W for mode-matching pump power of 110 m W, corresponding to 45% raw efficiency（56% net efficiency when considering the output coupling mirror’s 80% transmission）. This is the highest efficiency obtained at this wavelength in PPKTP with such low pump power. We obtain 80% beam coupling efficiency to single-mode fiber, demonstrating high beam quality.     

Characterization and comparison of 1% at Yb-doped Lu2O3 and Sc2O3 ceramics as laser gain media

We present the first laser oscillation achieved on Yb-doped Sc₂O₃ and Lu₂O₃ ceramics with a level of doping as low as 1 at %, under quasi-continuous wave pumping at 968 nm. Ceramic samples reached comparable performances in terms of tunability ranges, which exceeds 41 nm, and laser output powers. In particular, with the former sample emitting at 1040.5 nm we measured a maximum output power of 2.2 W with a corresponding slope efficiency of ?? = 59%. The latter medium delivered 1.8 W with a slope of ?? = 45% at 1032.5 nm while at 1078 nm we measured 1.5 W with ?? = 34%. Finally, we report the measured level of the Amplified Spontaneous Emission (ASE) for both samples, which was found to be less than 0.1 mW at the maximum pump power.     

High-power polycrystalline Er:YAG ceramic laser at 1617 nm

We report on the efficient operation of a high-power erbium-doped polycrystalline Er:YAG ceramic laser at 1617 nm resonantly pumped by a high-power 1532 nm Er,Yb fiber laser. Lasing characteristics of Er:YAG ceramics with different Er3+ concentrations are evaluated and compared. With an output coupler of 15% transmission and 0.5 at. % Er3+-doped YAG ceramic as the gain media, the laser generates 14 W of output power at 1617 nm for 28.8 W of incident pump power at 1532 nm, corresponding to a slope efficiency with respect to incident pump power of 51.7%.     

28.2 W波长锁定878.6 nm激光二极管共振抽运双晶体1064 nm激光器

报道了一种由波长锁定878.6 nm半导体激光器共振抽运两块不同掺杂浓度Nd:YVO4晶体串接的1064nm激光器,并与使用单块的低掺杂浓度晶体和高掺杂浓度晶体情况进行比较,实验表明利用波长锁定878.6nm半导体激光器共振抽运双晶体串接的方式,有利于降低晶体的热效应,提高光光转换效率.当抽运功率为40 W时,获得了28.2 W的1064 nm激光输出,光光转换率为70.5%,斜率效率为70.6%,相对吸收光的光光转换率76%,斜率效率为76.4%,同时该激光器在10?C—40?C的温度变化范围内具有极好的温度稳定性.     

Watt-level ~2 μm laser output in Tm3+-doped tungsten tellurite glass double-cladding fiber

We report, for the first time to the best of our knowledge, a watt level cw fiber laser at ~2 μm from a piece of 40-cm-long newly developed highly thulium-doped (3.76 × 10(20) ions/cm(3)) tungsten tellurite glass double cladding fiber pumped by a commercial 800 nm laser diode. The maximum output power of the fiber laser reaches 1.12 W. The slope efficiency and the optical-optical efficiency with respect to the absorbed pump are 20% and 16%, respectively. The lasing threshold is 1.46 W, and the lasing wavelength is centered at 1937 nm.     

Holmium laser in-band pumped by a thulium laser in the same host of YAlO3

We report on the room-temperature continuous-wave (CW) operation of a Ho:YAlO₃ laser that is resonantly end pumped at 1.94 μm by a diode-pumped thulium-doped laser in the same host. Through the use of a 1 at % Ho³⁺-doped 20-mm-long YAlO₃ crystal (b cut), the Ho:YAlO₃ laser generated 1 W of linearly polarized (E//c) output at 2118 nm and 0.55 W of E//a output at 2128.5 nm for an incident pump power of 5 W, with an output coupler transmission of 14 and 3%, respectively. An optical-to-optical conversion efficiency of 20% and a slope efficiency of 33% were achieved at 2118 nm corresponding to an incident pump power.     

Comparison of Laser Performances of 5at.% Yb:Gd2xY2(1-x)SiO5 Crystals between Different Cutting Directions

We investigate the laser actions of 5at.% Yb:Gd_2xY_2(1-x)SiO₅ (Yb:GYSO; x=0.1) crystals with different cutting directions, parallel and vertical to the growth axis. Our results show that the cutting direction of the sample plays an astonished role in the laser operation. The sample cut vertically to the growth axis possesses the favourable lasing characteristics. Its output power reaches 3.13W at 1060nm with a slope efficiency of 44.68% when the absorbed pump power is 8.9,W. In contrast, the sample cut parallel reaches only 1.65W at 1044nm with a slope efficiency of 33.76% with absorbed pump power of 7.99W. The absorption and emission spectra of the two samples are examined and the merit factor M is calculated. Our analysis is in agreement well with the experimental results. The wavelength tuning range of the superior sample covers from 1013.68nm to 1084.82nm.     

In-band pumped highly efficient Ho:YAG ceramic laser with 21 W output power at 2097 nm

We report on the high-power and high-efficiency operation of a polycrystalline Ho:YAG ceramic laser in-band pumped by a Tm fiber laser at ~1907 nm. Lasing characteristics of a 1.5 at.% and a 2.0 at.% Ho3?-doped YAG ceramic were investigated and compared. Using an output coupler of 6% transmission, over 21.4 W of cw output power at 2097 nm has been generated with the 1.5 at.% doped Ho:YAG ceramic under 35 W of incident pump power, corresponding to an average slope efficiency with respect to the incident pump power of 63.6% and an optical-to-optical conversion efficiency of 61.1%.     

10-W-level diode-pumped compact 2.78 microm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 mum from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.     

All-solid-state low noise Yb:YAG/LBO green laser at 515 nm

We report the efficient compact green laser at 515 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode-pumped Yb:YAG laser on the transition at 1030 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation (SHG) of the laser. With the incident pump power of 10 W, 270 mW of CW output power at 515 nm is achieved with 15-mm-long LBO. The optical-to-optical conversion efficiency is 2.7%, and the power stability in 8 h is better than 2.36% with low noise.     

Laser operation of Yb3+ in the acentric RbTiOPO4 codoped with Nb5+

We report on continuous-wave lasing of Yb(3+) at room temperature in the noncentrosymmetric RbTiOPO(4) crystal, codoped with Nb(5+), for all three possible polarizations. A maximum output power of 154 mW at 1050 nm was obtained for an absorbed power of 386 mW. The highest slope efficiency reached approximately 60% and the lowest threshold (with respect to the absorbed power) was 18 mW. The laser was tunable from 1009 to 1081 nm.     

激光二极管抽运Nd∶YVO4晶体1342nm和671nm激光器研究

报道了激光二极管抽运的Nd∶YVO₄晶体1342和671nm激光特性.1342nm激光最大输出功率为1.75W，光-光转换效率为32.1%，斜效率为43%.利用Ⅰ类非临界相位匹配LBO晶体腔内倍频，当输入抽运功率为6W时，获得功率为502mW的671nm激光输出，光-光转换效率超过8.3%；当671nm激光输出功率为400mW时，短期的不稳定度小于2%. 关键词：     

Diode-pumped high-power cw blue laser at 473 nm with a compact three-element cavity

We report on a diode-pumped cw Nd:YAG laser operating at 946 nm with a maximum output power of 3.3 W and a slope efficiency of 22% with respect to the incident pump power of 17.5 W. Intracavity frequency doubling with nonlinear crystal LBO yielded a single-ended blue output power of 590 mW with optical conversion efficiency of 3.4%. A very simple, compact three-element cavity of 35 mm long was used. The power fluctuation of the blue laser was 4.3% (rms) at output power level of 400 mW. Transverse mode hopping was observed at higher output power.     

Generation of 840 mW of red light by frequency doubling a diode-pumped 1342 nm Nd:YVO4 laser with periodically-poled LiTaO3

We report an efficient generation of red light in a periodically-poled LiTaO₃ (PPLT) crystal by extracavity single-pass frequency doubling of a diode-pumped, Q-switched Nd:YVO₄ laser at 1342 nm. The sample used in the experiment is 20 mm in length and 14.77 μm in period. An average power of 840 mW of the 671 nm red light is obtained with a 808 nm pump of 12.3 W, the overall optical-to-optical efficiency being 6.8%. The measured effective nonlinear coefficient of the sample is ∼3.8 pm/V. The high conversion efficiency and output power demonstrate that the periodically-poled crystal serving as a frequency conversion device may be used in practice to construct an all-solid-state red laser based on an extracavity single-pass quasi-continuous scheme. Received: 17 September 2001 / Revised version: 23 January 2002 / Published online: 8 May 2002