Laser characteristics of a new crystal Nd:Sr5(PO4)3F at 1.059 μm

The absorption spectrum of a new crystal Nd : Sr₅(PO₄)₃F or Nd : S-FAP, was measured, its two strong absorption peaks and broad effective absorption band showed that Nd : S-FAP can be appropriately pumped at 575 nm and 805.4 nm as well as with a xenon flashlamp. By using a tunable dye-laser (570.0~600.0 nm), a laser-diode (805 nm) and a xenon flash lamp as pump sources, respectively, the performance of a low threshold and high efficiency Nd:S-FAP laser at 1.059 (μm) (including pulse run, cw run, free-run and Q-switch run) has been demonstrated. The laser characteristics, such as the emission spectrum, the output energy, the output power, the pulse width, etc, were measured. In addition, the prospect of a Nd:S-FAP crystal for low-threshold high-efficiency miniature lasers is discussed.     

Diode-laser pumped 1.328 μm Nd:Sr5(PO4)3F miniature laser

Nd:Sr₅(PO₄)₃F, known as Nd:S-FAP, is a new material for efficient and miniature diode-laser pumped solid-state lasers. By using a laser-diode pump operating at 805.4 nm, Nd:S-FAP has been successfully lased at 1.328 μm. A slope efficiency of 33.5% and a laser threshold of 18.5 mW have been measured. The theoretical formulas for threshold power and slope efficiency were given and the theoretical estimation agreed with the experimental result.     

高效率低阈值Nd:S-FAP晶体激光特性

测量了新型晶体Nd:S-FAP[Nd:Sr₅(PO₄)₃F]的吸收光谱特性,它具有宽的有效吸收带,在575.0nm和805.4nm处有二个强的吸收峰.用可调谐染料激光器测量了575.0nm处的吸收系数为19.7cm^-1,用波长为575.0nm的的染料激光作泵浦源,实现了1.059μm的全偏振光输出,最低闽值为2.5mJ,斜效率为49%.用KTP倍频获得的绿光的波长为0.5295μm,峰值半宽度为1.0nm.     

染料激光泵浦Nd：S－VAP晶体激光特性研究

实验测定了Ｎｄ：Ｓｒ５（ＶＯ４）３Ｆ（简称Ｎｄ：Ｓ－ＶＡＰ）晶体的吸收光谱特性；在５８３．０ｎｍ和８０９．０ｎｍ处有强的吸收峰。用可调谐染料激光作泵浦源，实现了低阈值、高效率的激光运转。在透射率１５％的平面平行腔情况下，斜率效率为５０％，阈值为２ｍＪ。倍频光中心波长为５３６．０ｎｍ，线宽为１．４ｍｍ。本文还对Ｎｄ：Ｓ－ＶＡＰ晶体可作为ＬＤ泵浦的小型激光器的工作物质等问题进行了讨论。     

Laser Diode－end－pumped Laser Performance of Nd－doped Sr＿5（PO＿4）＿3F at 1059 and 1328 nm

ＬａｓｅｒＤｉｏｄｅ－ｅｎｄ－ｐｕｍｐｅｄＬａｓｅｒＰｅｒｆｏｒｍａｎｃｅｏｆＮｄ－ｄｏｐｅｄＳｒ＿５（ＰＯ＿４）＿３Ｆａｔ１０５９ａｎｄ１３２８ｎｍ￥ＳＵＮＬｉａｎｋｅ；ＺＨＡＮＧＳｈａｏｊｕｎ；ＣＨＥＮＧＲｕｐｉｎｇ；ＬＩＵＸｕｎｍｉｎ（Ｉｎｓｔ...     

Efficient blue emission of ytterbium-doped Sr<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F under quasi-three-level intracavity pumping

We report an Yb:Sr₅(PO₄)₃F (Yb:S-FAP) laser emitting at 985 nm intracavity pumped by a 912 nm diode-pumped Nd:GdVO₄ laser. A 808 nm diode laser is used to pump the Nd:GdVO₄ crystal emitting at 912 nm, and the Yb:S-FAP laser emitting at 985 nm intracavity pumped at 912 nm. With incident pump power of 17.5 W, intracavity second harmonic generation has been demonstrated with a power of 131 mW at 492.5 nm by using a LBO nonlinear crystal.     

新型晶体Nd:S-VAP激光特性研究

测量了 Nd:S-VAP[Nd:Sr₅(VO₄)₃F]晶体的吸收光谱特性,在583.0nm 和809.0nm处有强烈的吸收峰.用可调谐染料激光泵浦实现了低阈值、高效率的激光运转.在透射率15%的平-平腔情况下,斜率效率为50%,阈值2mJ,倍频绿光的中心波长为536.0nm,线宽为1.4nm.采用φ4mm×30mm 的氙灯泵浦,实现了自由运转和染料片调 Q 运转.阈值为130mJ,斜效率为1.3%.测量了不同腔长、不同染料片小信号透射率情况下的输出能量、脉冲宽度以及光束发散角和偏振特性等.     

Nd：S—FAP晶体1.328μm激光特性研究

用染料激光和氙灯泵浦实现了ＮｄＳ－ＦＡＰ晶体低阈值、高效率的１．３２８μｍｍ激光运转。在透过率７％的平－平腔情况下，染料激光泵浦斜效率为３８％，阈值４．５ｍＪ，倍频红光波长为０．６６４μｍ，线宽１．３ｎｍ；采用氙灯泵浦（４×３０ｍｍ），实现了１．３２８μｍ自由运转，阈值为２４０ｍＪ，斜效率为０．８５％。测量了不同腔长，不同透过率情况的输出能量、光束发散角和偏振特性等。     

Diode-pumped Nd:YVO(4)/Yb:S-FAP laser emitting at 985 and 492.5 nm

For the first time, to the best of our knowledge, Yb:S-FAP crystals have been intracavity pumped by a Nd:YVO(4) laser at 914 nm. This original pumping scheme allows efficient laser action on the three-level transition at 985 nm with 1.4 W output power. Second-harmonic generation is also presented with a total output power of 120 mW at 492.5 nm.     

Growth and laser properties of Nd:Ca4YO(BO3)3 crystal

Nd:Ca₄YO(BO₃)₃ (Nd:YCOB) crystal was grown by the Czochralski method, and its structure was measured by using a four circle X-ray diffractometer. The transparent spectrum from 200 to 2600 nm was measured at room temperature. The fluorescence spectrum near 1.06 μm showed that the main emission wavelength of Nd:YCOB crystal was centered at 1060.8 nm. Laser output at 1.06 μm has been demonstrated when it was pumped by a Ti:sapphire laser at the wavelength of 794 nm, the highest output power was 68 mW under pumping power of 311 mW, the pumping threshold was 163 mW and slope efficiency was 46.9%. The self-frequency doubled green light has been observed when it was pumped by a Ti:sapphire or a laser diode (LD). A 14.5 mm Nd:YCOB crystal sample cut at (θ, φ)=(90°, 33°) was used for type I second-frequency generation (SHG) of the 1.06 μm laser pulse. The SHG conversion efficiency was 22%.     

High-efficiency Nd:YVO4 laser emission under direct pumping at 880 nm

We report a high-efficiency Nd:YVO₄ laser pumped by an all-solid-state Q-switched Ti:Sapphire laser at 880 nm in this paper. Output power at 1064 nm with different-doped Nd:YVO₄ crystals of 0.4-, 1.0- and 3.0-at.% under the 880 nm pumping was measured, respectively. Comparative results obtained by the traditional pumping at 808 nm into the highly absorbing ⁴F_5/2 level were presented, showing that the slope efficiency and the threshold with respect to the absorbed pump power of the 1.0-at.% Nd:YVO₄ laser under the 880 nm pumping was 17.5% higher and 11.5% lower than those of 808 nm pumping. In a 4-mm-thick, 1.0-at.% Nd:YVO₄ crystal, a high slope efficiency of 75% was achieved under the 880 nm pumping, with an optical-to-optical conversion efficiency of 52.4%.     

Continuous-wave high-power multi-pass pumped thin-disc Nd:GdVO4 laser

A thin-disc Nd:GdVO₄ laser in multi-pass pumping scheme was developed. Continuous-wave output power of 13.9 W at 1.06 μm for an absorbed power at 808 nm of 22 W was demonstrated from a 250-μm thick, 0.5-at.% Nd:GdVO₄ in a 4-pass pumping; the slope efficiency in absorbed power was 0.65, or 0.47 in input power. Output performances were also investigated under diode laser pumping at 879 nm, directly into the emitting ⁴F_3/2 level: maximum power of 3.6 W was obtained at 6.2 W of absorbed power with 0.69 slope efficiency. Compared with pumping at 808 nm, into the highly absorbing ⁴F_5/2 level, improvements of laser parameter in absorbed power (increase of slope efficiency, decrease of threshold) were obtained, showing the advantages of the pumping into the emitting level. However, the laser performances expressed vs. the incident power were modest owing to the low absorption efficiency at 879 nm. Thus, increased number of passes of the medium would be necessary in order to match the performances in input power obtained under 808-nm pumping.     

Comparison of 885 nm pumping and 808 nm pumping in Nd:CNGG laser operating at 1061 nm and 935 nm

A Nd:CNGG laser operated at 935 nm and 1061 nm pumped at 885 nm and 808 nm, respectively, is demonstrated. The 885 nm direct pumping scheme shows some advantages over the 808 nm traditional pumping scheme. It includes higher slope efficiency, lower threshold, and better beam quality at high output power. With the direct pumping, the slope efficiency increases by 43% and the threshold decreases by 10% compared with traditional pumping in the Nd:CNGG laser operated at 935 nm. When the Nd:CNGG laser operates at 1061 nm, the direct pumping increases the slope efficiency by 14% with a 20% reduction in the oscillation threshold.     

锁模Yb：S—FAP激光器

本文首次报道了连续波Ｔｉ：Ｓａｐｐｈｉｒｅ纵向泵浦主动锁模Ｙｂ：Ｓ－ＦＡＰ激光器。实验得的最短锁模脉宽为３５．４ｐｓ，通过特殊设计的定态激发光谱实验，我们对它的锁模特性进行了研究，因为从理论上说Ｙｂ：ＹＳ－ＦＡＰ４ｎｍ的荧光线宽应能得到更短的变换极限脉宽。     

染料激光抽运Nd:YCOB自倍频激光器

Ｎｄ：ＹＣａ４Ｏ（ＢＯ３）３（简称Ｎｄ：ＹＣＯＢ）是一种新型自倍频激光复合功能晶体,利用Ｄａｔａｃｈｒｏｍ－５０００型染料激光器作为抽运源,横向抽运钕离子原子比为８％的Ｎｄ：ＹＣＯＢ获得了５３０．２ｎｍ绿色自倍频激光输出。在样品未镀膜的情况下阈值抽运量小于２ｍＪ,绿光输出能量最大为１．０３ｍＪ,能量转换效率约为３．３％。     

Laser emission in highly doped Nd:YAG crystals under (4)F(5/2) and (4)F(3/2) pumping

A comparison of laser emission in highly doped (2.4-and 3.5-at. %) Nd:YAG crystals is made for conventional 808-nm pumping in F(5/2)(4) and resonant pumping at 885 nm in the band that collects the hot transitions Z(2)?R(1) and Z(3)?R(2) of I(9/2)(4)?F(3/2)(4) absorption. A systematic improvement of the laser parameters (slope efficiency and emission threshold) in absorbed power under hot-band pumping is observed, as expected from the reduction of the pump's quantum defect. Together with the expected reduction of heat generation, resonant hot-band pumping in concentrated components shows prospect for greatly increasing the emission capabilities of the Nd:YAG lasers.     

Diode pumped Nd:GSAG and Nd:YGG laser at 942 and 935 nm

Two new Nd³⁺ doped crystals show laser activity between the ⁴F_3/2 and ⁴I_9/2 levels. Diode pumped emission of Nd:GSAG at 942 nm wavelength with 950 mW output power and 14% optical to optical efficiency as well as laser emission of Nd:YGG at 935 nm with 700 mW output power and 11% efficiency have been obtained. These wavelengths are useful for water vapour absorption measurements.     

Laser and absorption saturation measurements of Cr crystals, pumped by broadband pulsed 940 nm radiation

The characteristics of a 940 nm pumped Cr⁴⁺:forsterite laser have been investigated using a pulsed colour centre laser as the excitation source. Laser threshold, slope efficiency and temporal behaviour have been determined for high and low Cr⁴⁺ doped material. 940 nm pumping is found to be more efficient than 532 and 730–770 nm excitation. Discrepancies with 1064 nm pumping are attributed to excited state absorption. Absorption saturation measurements have been used to assess the potential applications of Cr⁴⁺:forsterite, Cr⁴⁺:YAG and Cr⁴⁺: Lu₃A1₅O₁₂ (LuAG) as passive Q-switches for Nd lasers in the 940 nm region.     

Nd3+:Er3+:KY(WO4)2激光晶体的生长和光谱特性

采用熔盐法从K2 WO4助熔剂体系生长出尺寸为 4 5mm的Nd3 :Er3 :KY(WO4) 2 透明晶体。从晶体中切割出Ф3× 11 9mm的激光器件 ,测量了晶体的紫外 -近红外的吸收光谱 ,从吸收光谱图上可以看到 ,晶体存在着 974 88nm ;80 1 0 (798 12 ,80 3 95 )nm ;74 8 5 (75 3 5 ,74 3 4 9)nm ;6 5 3 6 1nm ;5 86 6 5nm ;5 18 6(5 4 5 0 3,5 2 1 32 ,4 89 35 )nm ;4 5 2 80nm ;4 0 7 81nm ;36 7 2 2 (377 2 4 ,36 6 4 ,35 8 0 2 )nm九个吸收峰带 ,对各个吸收峰带按照Er3 和Nd3 离子的能级跃迁进行了归属。同时采用Edinburgh InstrumentF92 0荧光光谱仪在室温下对晶体进行了荧光测试研究。研究结果表明 ,共掺Nd3 离子可以增强Er3 :KY(WO4) 2 对半导体激光器泵浦源 (80 0nm)的吸收。     

Three-level operation of a diode-bar-pumped Yb:S-FAP laser

We present an all solid-state Yb:S-FAP laser system running on the three-level laser transition at 985 nm. The pump source was a high fill-factor laser diode bar, with the output reformatted using a two-mirror beamshaping system to produce a rectangular pump beam that focused to a square spot. A nearly on-axis multipassing system was used to obtain four pump passes through a 1.6 mm Yb:S-FAP laser crystal. Gain-switched three-level laser output was achieved with an efficiency of 4.3% with respect to incident pump power. Electro-optic Q-switching produced 0.12 mJ pulses for a pump pulse energy of 11 mJ. Intra-cavity second-harmonic generation yielded a maximum pulse energy at 492.5 nm of 12 μJ.