Study on the second-harmonic-generation of GdCa4O(BO3)3 crystals along various phase-matching directions

In this paper, the theoretical calculations of d_eff of GdCa₄O(BO₃)₃ (GdCOB) along various phase-matching (PM) directions are reported. It is shown that the maximum d_eff is out of the main planes and the d_eff in the range of (0<θ≤90, 90<φ≤180) are larger than that in the range of (0<θ≤90, 0≤φ≤90). The PM direction along (θ=66.8, φ=132.6) for GdCOB crystal has the largest d_eff. Second-harmonic-generation (SHG) experiments were performed on GdCOB crystal along various PM directions. The results show that in GdCOB crystal, the intracavity SHG conversion efficiency is 27.6% along the PM direction (θ=66.8, φ=132.6) which is larger than that along PM directions in XY and XZ main planes, which are in good agreement with the theoretical calculations. The continuous-wave (cw) green laser output power is 1.22 W when LD pump power is 10 W in the Nd:YVO₄/GdCOB laser.     

Intracavity second-harmonic generation of 1.06 μm in GdCa4O(BO3)3 crystals

The characteristics of intracavity second-harmonic generation (SHG) at 1.06 μm in GdCa₄O(BO₃)₃ (GdCOB) crystals cut for different type I phase-matching (PM) directions of (θ,φ)=(66.8°, 132.3°); (19.4°, 0°); (90°, 46°) have been investigated. It was found that the intracavity SHG was significantly efficient in the PM direction of (66.8°, 132.3°), and that the intrinsic lower effective nonlinear coefficient (d_eff) was responsible for the less-efficient SHG in the other two directions. A maximum CW SHG output power of 2.81 W was obtained with an optical conversion efficiency of 18.7%, while the corresponding effective intracavity SHG efficiency was determined to be 41.3%. The intracavity SHG efficiency of GdCOB has been found to reach two-thirds of that obtained with type II phase-matching KTiOPO₄ (KTP). Received: 26 April 2000 / Revised version: 3 July 2000 / Published online: 5 October 2000     

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%.     

Second harmonic generation from precise diamond blade diced ridge waveguides

Carbon ion irradiation and precise diamond blade dicing are applied to fabricate Nd:GdCOB ridge waveguides. The propagation properties of the fabricated Nd:GdCOB waveguides are investigated through experiments and theoretical analysis. Micro-Raman analysis reveals that the Nd:GdCOB crystal lattice expands during the irradiation process. Micro-second harmonic spectroscopic analysis suggests that the original nonlinear properties of the Nd:GdCOB crystal are greatly enhanced within the waveguide volume. Under pulsed 1064 nm laser pumping, second harmonic generation (SHG) at 532 nm has been achieved in the fabricated waveguides. The maximum SHG conversion efficiencies are determined to be ～ 8.32 %·W^-1 and ～ 22.36 %·W^-1 for planar and ridge waveguides, respectively.     

All-solid-state continuous-wave frequency-doubling Nd:LuVO<Subscript>4</Subscript>/GBCOB laser at 533 nm

We report an efficient intracavity second-harmonic generation (SHG) at 1066 nm in a non-linear optical crystal, GdCa₄O(BO₃)₃ (GdCOB), performed with a diode end pumped continuous-wave (CW) Nd:LuVO₄ laser. In the case of a laser with a Nd:LuVO₄ crystal frequency-doubled with a GdCOB crystal cut for type I frequency doubling. A CW SHG output power of 5.18 W has been obtained using a 10 mm long GCOB crystal. The optical conversion efficiency with respect to the incident pump power was 28.5%.     

偏硼酸钡低温相的晶体结构

本文报道了新型信频材料——偏硼酸钡[Ba₃(B₃O₆)₂]低温相的晶体结构。晶体属三方晶系,空间群为C₃⁴-R3,取六方坐标系,晶胞参数为a=b=12.532?,c=12.717?,z=6。在PhilipsPW-1100四圆衍射仪上收集到独立衍射693个。采用重原子法通过三维帕特逊和三维傅里叶合成测定结构,并用对角矩阵最小二乘法修正至R=0.046。该晶体是一个由Ba²⁺和(B₃O₆)^3-环交错组成的层状阶梯式结构。其阴离子(B₃O₆)^3-环基本上是平面状的。基团平面垂直于三次轴;Ba²⁺近邻有7个氧原子。将此结构与偏硼酸钡高温相比较表明,由于钡阳离子的非中心对称分布改变了阴离子硼氧环共轭基团的电子云密度,这一结构上的变化对该晶体的倍频效应做了主要贡献。 关键词：     

Passively Q-switched self-frequency doubling Nd:Ca4GdO(BO3)3 laser with Cr:YAG saturable absorber

Nd³⁺ : Ca₄GdO(BO₃)₃, known as Nd : GdCOB, is a new self-frequency doubling laser crystal. Using Cr⁴⁺ : YAG as passive Q-switch, we have realized the Q-switched laser running at 0.53 μm with an Nd : GdCOB crystal. Meanwhile, the pulse width, the single pulse energy and the repetition rate under different small-signal transmission of Cr⁴⁺ : YAG and different pump conditions are measured and the numerical solutions of the coupling wave rate equations agree with the experimental results.     

Efficient intracavity second-harmonic generation at 1063 nm in a GdCOB crystal

We report an efficient intracavity second-harmonic generation (SHG) at 1063 nm in a non-linear optical crystal, GdCa₄O(BO₃)₃ (GdCOB), performed with a diode end pumped continuous-wave (CW) Nd:GdVO₄ laser. In the case of a laser with an a-cut 0.4 at % Nd:GdVO₄ crystal frequency-doubled with a GdCOB crystal cut for Type I frequency doubling. A CW SHG output power of 2.25 W has been obtained using a 15 mm long GCOB crystal. The optical conversion efficiency with respect to the incident pump power was 12.4%.     

Second-order optical nonlinearity in bulk PbO/B2O3 glass

By investigating the second-harmonic generation (SHG) of the bulk PbO/B₂O₃ glass samples with different compositions after thermal poling, it was found that there was an optimal poling temperature for each sample with different compositions and there was also a relation between optimal poling temperature and glass transition temperature. At their own optimal poling temperatures, the samples had different frequency doubling efficiencies with the same applied voltage. We also found that the frequency doubling efficiency of PbO/B₂O₃ glass increased with the increase of poling voltage. An induced dipole model was proposed to explain the super-quadratic relation between the SHG intensity and the poling voltage.     

波长锁定878.9nm激光二极管抽运内腔式YVO_4/BaWO_4连续波拉曼激光器

采用波长锁定878.9 nm激光二极管共振抽运复合Nd:YV04激光晶体,改善热效应的同时提高抽运吸收率,分别以YVO_4和BaWO_4晶体作为拉曼介质,实验和理论研究了晶体性能、谐振腔结构和稳定性对内腔分体式连续波拉曼激光器性能的影响.结果表明:由于内腔分体式拉曼激光器腔长较长,谐振腔稳定性对激光器性能影响较大,选择高增益的拉曼晶体,不仅可获得高拉曼转换效率,还能一定程度上减轻热效应.而平凹腔结构中输出镜的曲率半径越小,拉曼晶体中基频光的功率密度越大,腔的动态稳定区越宽,获得的拉曼激光输出功率更高.最终以30 mm的BaWO_4晶体作为拉曼介质,在抽运功率25.1 W时,获得了3.02 W的连续拉曼激光输出,光-光转换效率达到12%.     

Compact efficient optical parametric generator internal to a Q-switched Nd:YVO4 laser with periodically poled MgO:LiNbO3

This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVO$_{4}$ laser with periodically poled MgO:LiNbO₃(PPMgLN). With the Q-switch set at a repetition rate of 25kHz and the PPMgLN crystal operated at room temperature (25\du\,), the intracavity optical parametric generator threshold was reached as a diode pump power of 0.9\,W. A maximum signal output power of 0.34W with a pulse width of 25\,ns and a beam quality factor of 1.4 was obtained at an incident diode power of 3.4\,W, leading to a conversion efficiency of 10{\%} with a slope efficiency of 14.4{\%}. By varying the crystal temperature from 25 to 200\du, the output signal wavelengths were tuned in range of 1506--1565\,nm. Over a 30-minutes interval, the instability of the signal power was measured to be less than 1{\%}. In addition, the threshold pump intensity for the intracavity optical parametric generator is theoretically investigated, and the obtained result is in good agreement with the experimental results.     

激光自倍频晶体研究和应用进展

激光自倍频晶体是一类同时具有激光和非线性效应的复合功能晶体。以激光自倍频晶体制作的全固态激光器具有体积小,调整方便,稳定性高等优点。自1970年代以来,以LiNbO3,YAl3(BO3)4倍频晶体为基质的激光自倍频晶体实现了自倍频激光运转。近年来,以RECa4O(BO3)3(RECOB)为基质的激光自倍频晶体受到重视和广泛研究。本文从对激光晶体、非线性光学晶体及激光自倍频晶体的基本要求出发,在综述激光自倍频晶体研究历史的基础上,讨论了激光自倍频晶体中的基波和倍频光,探讨了NYAB和Nd:GdCOB一类晶体中晶体长度,Nd3+浓度和效率之间的关系。理论估算表明,当浓度适当,晶体长度10mm时,这两类晶体的光–光转换效率可达30%以上。本文总结了NYAB系列晶体的研究历程及RECOB系列激光自倍频研究的思路及取得的成果。在最近10年中,利用山东大学生长的Yb:YAB晶体,获得1.1 W自倍频绿光,光光转换效率为10%;在RECOB体系中,比较了各种晶体的特点,选定Nd:GdCOB为主要研究对象,经过晶体掺钕浓度和长度关系,位相匹配方向、膜系及热工程等多方面研究,获得了1.36 W的545 nm绿光输出,光–光转换效率为17.1%;输出功率为1.03 W时,半小时功率波动不超过1%。这是目前为止,Nd3+离子激光自倍频晶体的最好结果。文章最后介绍了激光自倍频晶体的可能应用。通过理论和实验分析,认为到目前为止Nd:GdCOB是以Nd3+为激活离子最后的激光自倍频晶体,而在Yb3+为激活离子时,Yb:YAB晶体最佳。     

LiIO3-Zn(IO3)2 赝二元系的研究

用固态粉末烧结法配制样品,用X射线衍射及差热分析等方法研究并测定了LiIO₃-Zn(IO₃)₂赝二元系的相图。该二元系内存在一新相LiZn(IO₃)₃。它有较大的倍频效应,具有离子导电性。用自编的由粉末衍射数据求单斜晶系的点阵参数的计算机程序成功地求出了该化合物的点阵常数。经过进一步修正,确定它属于正交晶系,α=8.08l?,b=8.729?,c=11.595?,z=4。并确定了化合物存在的成分范围和条件。 关键词：     

正磷酸盐晶体Ba3(PO4)2和Sr3(PO4)2高温拉曼光谱研究

测量了碱土金属正磷酸盐Ba₃(PO₄)₂和Sr₃(PO₄)₂常温及高温拉曼光谱, 对拉曼振动模式进行指认, 并分析了晶体拉曼振动光谱及晶体结构在高温下的变化. 在温度升高的过程中, 拉曼振动频率向低频移动且振动峰宽度展宽, 晶体中的P-O平均键长随温度升高而变长, 但O-P-O的键角并未发生变化. 晶体在900 ℃以下无结构相变发生. 关键词： 3(PO₄)₂和Sr₃(PO₄)₂')" href="#">Ba₃(PO₄)₂和Sr₃(PO₄)₂ 高温拉曼光谱 振动模式 高温结构     

Li2K(IO3)3与Li2NH4(IO3)3的晶体结构

本文用X射线粉末法测定了Li₂K(IO₃)₃与Li₂NH₄(IO₃)₃的晶体结构和原子参数。发现Li₃K(IO₃)₃,Li₂NH₄(IO₃)₃与Li₂Rb(IO₃)₃同晶型,属单斜晶系,空间群为P2₁/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。 关键词：     

Li掺杂对MgH2(001)表面H2分子扩散释放影响的第一性原理研究

本文利用基于密度泛函理论的第一性原理分别研究了MgH₂(001)表面H原子扩散形成H₂分子释放出去的可能路径及金属Li原子掺杂对其影响. 研究结果表明: 干净MgH₂(001)表面第一层释放H原子形成H₂分子有两种可能路径, 其释放能垒分别为2.29和2.50 eV; 当将Li原子替代Mg原子时, 两种H原子扩散释放路径的能垒分别降到了0.31和0.22 eV, 由此表明Li原子掺杂使MgH₂(001)表面H原子扩散形成H₂释放更加容易.     

Efficient Nd:Y0.5Gd0.5VO4-KTiOPO4 green laser under diode pumping into the emitting level 4F3/2

We report a green laser at 532 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1064 nm Nd:Y_0.5Gd_0.5VO₄ laser under diode pumping into the emitting level ⁴ F _3/2. A KTiOPO₄ (KTP) crystal, cut for critical type-II phase matching at room temperature is used for second harmonic generation (SHG) of the laser. At an incident pump power of 17.8 W, as high as 4.21 W of cw output power at 532 nm is achieved. The optical-to-optical conversion efficiency is up to 23.6%, and the fluctuation of the green output power was better than 2.8% in the given 30 min.     

Dy^(3+)掺杂Lu_(2)O_(3)和Y_(2)O_(3)单晶光纤下转换荧光测温性能EI北大核心CSCD

稀土倍半氧化物单晶光纤材料凭借超高的熔点(~2400℃)、稳定的物化性能以及灵活的结构被认为是极具潜力的高温传感介质。本文采用激光加热基座(LHPG)法,成功生长了透明无开裂Dy^(3+)离子掺杂的倍半氧化物单晶光纤Lu_(2)O_(3)和Y_(2)O_(3)。依据Dy^(3+)离子的^(4)I_(15/2)和^(4)F_(9/2)能级为一对热耦合能级对(TCLs),测试得到了430~520 nm波长范围内的下转换荧光光谱。荧光强度比(FIR)结果显示,晶体在298~673 K温度范围内的荧光强度具有良好的温度相关性。其中Dy∶Lu_(2)O_(3)在该范围内的最大相对灵敏度和绝对灵敏度分别为0.97%·K^(-1)(315 K)和1.62×10^(-4) K^(-1)(673 K),展现出更为优异的温度传感性能。     

Large energy 1341.4 nm Nd: YALO3 pulse laser

On the basis of a measured stimulated emission cross-section for the ⁴F_3/2-⁴I_13/2 transition of the Nd³⁺ ion in a YAP crystal, it is shown that the Nd:YALO₃ crystal is a useful kind of laser crystal to operate in a pulsed laser at 1341.4 nm. Output energy of 5.31 J with an overall efficiency of 1.84% at 1341.4 nm has been achieved by using a 6 mm diameter and 101 mm long A-axis YALO₃ rod with 1 at.% Nd³⁺ ion.     

准一维Cr基超导体RbCr3As3的超导能隙

RbCr₃As₃是具有[（Cr₃As₃）^-]_∞线性链的准一维超导体,超导转变温度约为6.6 K.对RbCr₃As₃单晶进行了电输运和极低温热输运性质的研究.低温下,拟合了RbCr₃As₃正常态电阻率随温度的变化,发现其满足费米液体行为.通过拟合超导转变温度随磁场的关系,得到RbCr₃As₃单晶的上临界场约为25.6 T.对RbCr₃As₃进行了零场下的极低温热导率测量,得到其剩余线性项为7.5 μW·K^-2·cm^-1,占正常态热导率值的24%.测量不同磁场下RbCr₃As₃的热导率,发现与单带s波超导体相比较,RbCr₃As₃剩余线性项随磁场增加相对较快.这些结果表明RbCr₃As₃单晶很可能是有节点的非常规超导体.