Ho:YVO_4晶体中Ho~(3+)光谱参数的计算

根据Ho3+在Ho :YVO4 晶体的吸收谱和 0 6～ 2 1μm波段的荧光谱 ,用J O理论计算了Ho3+的强度参数Ωλ ,并由此计算了激发能级的振子强度、自发辐射跃迁几率、荧光分支比和积分发射截面等光谱参数 ,讨论了Ho :YVO4 晶体作为红外激光材料的可能性。     

Tm，Ho双掺杂YV04晶体中Tm对Ho敏化发光现象

摘要：报道了对Tm,Ho双掺YVO4晶体光谱性能的测量结果,包括用UV-365型分光光度计测出单掺Tm：YVO4及Ho：YVO4吸收谱以及双掺Tm：Ho：YVO4的吸收谱;用Ar离子激光器488nm,LD激光器激发测量样品荧光光谱;用J-O理论进行光谱参数计算及对能级结构进行分析;研究了在λ=805nm的激光二极管激发下Tm对Ho的敏化发光过程。发现与YAG,YLF为基质的Tm,Ho双掺材料相比,该材料中的Tm3+离子具有大而均匀的吸收宽度(～26nm),大的峰位吸收截面和积分吸收截面(～1.4×10-20cm2和274.5×10-20 cm),能量转换效率高(可达87％),且泵浦阈值低(～15mW)。表明了YVO4晶体中Tm能有效地敏化Ho,并产生2μm的发射。文中对发射强度与泵浦功率及Tm,Ho之间掺杂浓度的关系进行了初步的分析与讨论。光谱的观察结果表明：在实现LD泵浦,全固体化,小型,高效的,2μm激光振荡的探索中,Tm：Ho：YVO4晶体将是一种很有实际应用潜力的材料。     

Tm,Ho双掺杂YVO_4晶体中Tm对Ho敏化发光现象

报道了对Tm ,Ho双掺YVO4 晶体光谱性能的测量结果 ,包括用UV 3 65型分光光度计测出单掺Tm∶YVO4 及Ho∶YVO4 吸收谱以及双掺Tm∶Ho∶YVO4 的吸收谱 ;用Ar离子激光器 4 88nm ,LD激光器激发测量样品荧光光谱 ;用J O理论进行光谱参数计算及对能级结构进行分析 ;研究了在λ=80 5nm的激光二极管激发下Tm对Ho的敏化发光过程。发现与YAG ,YLF为基质的Tm ,Ho双掺材料相比 ,该材料中的Tm3 + 离子具有大而均匀的吸收宽度 (～ 2 6nm) ,大的峰位吸收截面和积分吸收截面 (～ 1 4× 1 0 -2 0 cm2 和 2 74 5× 1 0 -2 0cm) ,能量转换效率高 (可达 87% ) ,且泵浦阈值低 (～ 1 5mW )。表明了YVO4 晶体中Tm能有效地敏化Ho,并产生 2 μm的发射。文中对发射强度与泵浦功率及Tm ,Ho之间掺杂浓度的关系进行了初步的分析与讨论。光谱的观察结果表明∶在实现LD泵浦 ,全固体化 ,小型 ,高效的 ,2 μm激光振荡的探索中 ,Tm∶Ho∶YVO4 晶体将是一种很有实际应用潜力的材料。     

单、双掺钒酸钇晶体的Raman光谱与能量转移研究

文章采用双光栅单色仪(HRD-1),氩离子激光器的488.0 nm波长激发,分别测得室温下,激发光平行、垂直晶体c轴入射时,Tm3 ,Ho3 单掺和双掺钒酸钇晶体的拉曼光谱,对检测结果进行分析并探讨了对能量转移的影响.观测到对Ho3 :YVO4,激发光垂直c轴时的散射光强明显强于激发光平行c轴时的散射光强;由于488.0 nm波长靠近Ho3 的一个吸收峰,吸收和散射相互竞争,使475 cm-1被削弱,且外模振动展宽;测得样品最大声子能量集中在880cm-1附近.主要是(VO4)3-的A1g呼吸模引起的,表明与YAG基质一样,也是一种具有高声子能量的晶体.用808 nm激发,锁相放大器,PbS探头接收,测得双掺Tm3 :Ho3 :YVO4的2.09 μm荧光强度是单掺Tm3 ∶YVO4 1.85 μm的4/5,意味着Tm3 对Ho3 的敏化效率高达80%,因为Tm3 :YVO4的荧光谱与Ho3 吸收谱重合甚少,由辐射跃迁导致的能量转移可能性不大,因此Tm3 离子之间的交叉弛豫以及Tm3 的3F4与Ho3 的5I7之间近共振的能量转移主要是依靠声子辅助的无辐射跃迁.     

Ho3+:LiYF4晶体的中红外发光特性

用坩埚下降法制备了Ho3+离子掺杂的LiYF4单晶。测定了Ho3+:LiYF4晶体的偏振吸收光谱。应用Judd-Ofelt理论分别计算了Ho3+:LiYF4晶体中Ho3+离子的有效强度参数Ω2,4,6、能级跃迁振子强度fexp和fcal、自发辐射跃迁几率A、荧光分支比β、辐射寿命τrad等光谱参数。测定了样品在640 nm光激发下的红外发射光谱,观测到由Ho3+离子的5I6→5I7跃迁所致的2.8～3μm中红外发光,以及在1.2μm(5I6→5I8)和2.0μm(5I7→5I8)处较强的荧光。Ho3+:LiYF4单晶样品的吸收峰线宽较宽,计算得到1.2μm和2.0μm的峰值发射截面分别达到0.20×10-20cm2和0.51×10-20cm2,同时测定了1 191 nm(5I6→5I8)和2 059 nm(5I7→5I8)发射的荧光寿命。研究结果表明:Ho3+:LiYF4晶体在2.0～3μm波段的中红外激光器中有较大的应用前景。     

Nd:YVO4激光晶体Raman光谱的分析

根据商群对称性分析法对Nd :YVO4 晶体的Raman光谱做了理论计算和指认 ,运用实验的手段 ,根据谱线数目判定其合理性 ,同时断定晶体原胞中含有 4个Nd :YVO4 分子     

HoYb:YVO4的上转换发光研究

研究了960nm激光激发下HoYb双掺钒酸钇晶体HoYb:YVO4的直接上转换增敏发光,发现了Ho3+离子的上转换发光现象,HoYb:YVO4晶体的上转换发光是5F5→5I8最强,而5S2→5I8相对小了一个数量级,这是由于YVO4晶体既有很强的振子强度又有很大的多声子无辐射弛豫造成的. 关键词： 上转换发光 直接增敏(敏化) 钒酸钇YVO4晶体 Ho3+离子     

Tm:YVO4晶体的光谱参数计算

由测量的Tm :YVO4晶体的吸收光谱 ,考虑到单轴晶体在各个方向上的吸收不同和折射率随波长的变化 ,根据Judd Ofelt理论计算了Tm3 +在YVO4中的强度参数、各个能级的振子强度、自发辐射几率、荧光分支比、积分发射截面等参数。强度参数为Ω2 =1 9416× 10 - 2 0 (cm2 ) ,Ω4=0 15 6 8× 10 - 2 0 (cm2 ) ,Ω6=0 396 3× 10 - 2 0 (cm2 )。计算结果表明 ,1 D2 → 3 F4的跃迁几率远大于1 D2 向其他各个能级的跃迁几率     

Tm,Ho双掺杂YVO4晶体中Tm对HO敏化发光现象

摘要报道了对Tm,Ho双掺YVO4晶体光谱性能的测量结果,包括用UV-365型分光光度计测出单掺TmYVO4及HoYVO4吸收谱以及双掺TmHoYVO4的吸收谱;用Ar离子激光器488nm,LD激光器激发测量样品荧光光谱;用J-O理论进行光谱参数计算及对能级结构进行分析;研究了在λ=805nm的激光二极管激发下Tm对Ho的敏化发光过程。发现与YAG,YLF为基质的Tm,Ho双掺材料相比,该材料中的Tm3+离子具有大而均匀的吸收宽度(～26nm),大的峰位吸收截面和积分吸收截面(～1.4×10-20cm2和274.5×10-20 cm),能量转换效率高(可达87％),且泵浦阈值低(～15mW)。表明了YVO4晶体中Tm能有效地敏化Ho,并产生2μm的发射。文中对发射强度与泵浦功率及Tm,Ho之间掺杂浓度的关系进行了初步的分析与讨论。光谱的观察结果表明在实现LD泵浦,全固体化,小型,高效的,2μm激光振荡的探索中,TmHoYVO4晶体将是一种很有实际应用潜力的材料。     

Er3+:YVO4中Er3+的光谱参数计算

根据掺杂Er3+(0.5%)的YVO4样品的吸收光谱,用Jubb-Ofelt理论拟合出唯象强度参最Ωλ,并由此计算了激发能级的振子强度、自发辐射跃迁速率、荧光分支比和积分发射截面等光谱参量.并根据这些光学参量,分析了Er3+:YVO4晶体的应用价值.其中,特别是4I13/2→4I15/2, 2H11/2→4I15/2, 4S3/2→4I15/2和4F9/2→4I15/2等几个强发光能级具有较大的振子强度(大于10-6)和积分发射截面(大于10-18cm),分别分析了它们的应用前景,因此非常值得关注.并且,本文结果和Capobianco等所报道的Er3+(2.5 mol%):YVO4晶体强度参量结果很相近.而且,通过比较掺Er3+钒酸钇晶体和掺Er3+其他晶体的光学性能,可以看出钒酸钇晶体作为激光晶体的优点.最后,还根据Er3+在晶体中的对称性,利用群论讨论了Er3+在YVO4晶场中各能级的劈裂情况.     

Ho3+/Tm3+共掺Ge-Ga-S-CsI玻璃的2.0μm中红外发光特性的研究

用熔融急冷法制备了系列Ho3+/Tm3+共掺的78GeS2-12Ga2S3-10Csl玻璃样品,测试了样品的吸收光谱以及808 nm激光泵浦下的2μm中红外荧光光谱.用Judd-Ofelt理论计算了Ho3+离子在78GeS2-12Ga2S3-10CsI硫卤玻璃中的强度参数Ω(i=2,4,6)、自发辐射跃迁概率Arad和...     

The Spectroscopic Properties of Tm and Ho Co-doped YVO4 Crystal

In this paper, the measured results of spectroscopic properties for Tm, Ho co-doped YVO4 crystals are reported. The absorption spectra, fluorescence spectra and calculated spectroscopic parameters are given. The processes of sensitized luminescence of Ho3+ by Tm3+ with 805 nm LD pumping were investigated. It was found that Tm3+ ion in YVO4 has a larger uniform absorption width (～26 nm) and a larger peak and integreted cross-section of absorption at 800nm (～1.4×10-20 cm2 and 246×10-20 cm) than that in YAG and YLF. The high energy transfer efficiency from Tm3+ to Ho3+ (up to 87%) and low pumping threshold (15 mW) show that Tm3+ can efficiently sensitize Ho3+ in YVO4 crystal. The dependence of ～2 μm emission for Ho3+ on the Tm, Ho doping concentrations was preliminarily analyzed and discussed.     

The Spectroscopic Properties of Tm and Ho Co-doped YVO_4 Crystal

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The Ho thickness dependence of spin-triplet supercurrents in Nb/Ho/Co/Ho/Nb films

Robinson et al. [J.W.A. Robinson, et al., Science 329 (2010) 59] reported control of spin-triplet supercurrents into ferromagnets by varying the thicknesses of the Ho injector and attributed the voltage peaks to non-integer spiral wavelengths of λ/2 and 5λ/2 in Ho. Here we demonstrate that these peaks correspond to λ/2 and 3λ/2.     

Energy levels and transitions in165Ho from neutron scattering

The¹⁶⁵Ho (n, ń) and¹⁶⁵Ho (n, ń γ) reactions were utilized to obtain information on the energy levels of¹⁶⁵Ho up to about 1400 keV excitation. A Ge (Li) detector was used in the time-gated mode to measure the de-excitation γ-rays. Neutrons were detected by a conventional time-of-flight spectrometer. Results from the two sets of measurements are combined to construct an energy level scheme for¹⁶⁵Ho. The level scheme is compared with results from other sources and some new levels are proposed.     

Thermal expansion of single crystal Tb-50% Ho

Data for the temperature variation of the c-axis strain in annealed Tb-50% Ho is compared with previous measurements on Tb-50% Ho and Dy. Although there is agreement near 273 K, it is considered that internal strain is responsible for deviations between present and previous data for Tb-50% Ho in the temperature range T_C < T < T_N. The data from annealed Tb-50% Ho and Dy are significantly different.     

Directly diode-pumped high-energy Ho:YAG oscillator

We report on the high-energy laser operation of an Ho:YAG oscillator resonantly pumped by a GaSb-based laser diode stack at 1.9 μm. The output energy was extracted from a compact plano-concave acousto-optically Q-switched resonator optimized for low repetition rates. Operating at 100 Hz, pulse energies exceeding 30 mJ at a wavelength of 2.09 μm were obtained. The corresponding pulse duration at the highest pump power was 100 ns, leading to a maximum peak power above 300 kW. Different pulse repetition rates and output coupling transmissions of the Ho:YAG resonator were studied. In addition, intracavity laser-induced damage threshold measurements are discussed.     

Nature of Ho magnetism in multiferroic HoMnO3

Using x-ray resonant magnetic scattering and x-ray magnetic circular dichroism, techniques that are element specific, we have elucidated the role of Ho3+ in multiferroic HoMnO3. In zero field, Ho3+ orders antiferromagnetically with moments aligned along the hexagonal c direction below 40 K, and undergoes a transition to another magnetic structure below 4.5 K. In applied electric fields of up to 1 x 10(7) V/m, the magnetic structure of Ho3+ remains unchanged.     

A comparison of resonantly pumped Ho:YLF and Ho:LLF lasers in CW and Q-switched operation under identical pump conditions

Singly 0.5 at.% Ho doped crystals of YLiF₄ (YLF) and LuLiF₄ (LLF) are studied under identical pump conditions in continuous-wave (CW) and Q-switched operation. Longitudinal end-pumped CW laser performance shows Ho:LLF to have a slightly lower threshold and a slightly higher slope efficiency with respect to absorbed pump power than Ho:YLF. Both lasers were operated on π-polarization. At a cavity output coupling of 20% and a crystal length of 30 mm, the Ho:LLF (Ho:YLF) laser yielded 18.8 W (18 W) of CW output at a wavelength of 2067.8 nm (2064.0 nm) for 41.4 W (42.2 W) of absorbed pump power with a slope efficiency of 67.1% (65.6%) and an optical-to-optical efficiency of 45.4% (42.6%) with respect to absorbed pump power. With the same output coupling and a crystal length of 40 mm, the Ho:LLF (Ho:YLF) laser yielded 20.5 W (18.1 W) of CW output at a wavelength of 2067.7 nm (2064.3 nm) for 51.5 W (50.0 W) of absorbed pump power with a slope efficiency of 58.4% (55.4%) and an optical-to-optical efficiency of 39.8 (36.1%) with respect to absorbed pump power. The influence of the temperature of the cooling mount on CW laser performance was studied and showed very similar results for both laser materials. At full pump power, a slope of −155 mW/°C (−149 mW/°C) was observed for the Ho:LLF (Ho:YLF) laser with a crystal length of 30 mm. In Q-switched operation, the Ho:LLF (Ho:YLF) laser produced 37 mJ (38.5 mJ) at a repetition rate of 100 Hz with a pulse duration of 38 ns (35 ns) at a wavelength of 2053.1 nm (2050.2 nm) with a slope efficiency of 30.3% (31%) and an optical-to-optical efficiency of 14.2% (13.9%) with respect to absorbed pump power. The beam quality was nearly diffraction limited (M ²<1.1).     

Review of Tm and Ho materials; spectroscopy and lasers

A review of Tm and Ho materials is presented, covering some fundamental aspects on the spectroscopy and laser dynamics in both single and co-doped systems. Following an introduction to 2-μm lasers, applications and historical development, the physics of quasi-four level lasers, energy transfer and modeling are discussed in some detail. Recent developments in using Tm lasers to pump Ho lasers are discussed, and seen to offer some advantages over conventional Tm:Ho lasers. This article is not intended as a complete review, but as a primer for introducing concepts and a resource for further study.