Multiphonon relaxation of rare earth ions in borate,phosphate, germanate and tellurite glasses

Non-radiative multiphonon relaxation rates were obtained for excited electronic states in borate, phosphate, germanate and tellurite glasses. The rates were calculated from the intensities of fluorescence in the visible range of the spectrum, the measured radiative transitions and the decay times of fluorescence. A functional dependence was found between the relaxation rates and the energy gaps of the rare earth ion. It was shown that by changing the glass host from the borate to tellurite matrix, an increase in visible fluorescence was achieved. This was especially notable in Er³⁺, where the increase of fluorescence from germanate to tellurite was by a factor of 15.     

YLiF4: Er3+, Tm3+, Yb3+中Tm3+浓度对上转换发光的影响

利用水热法合成了YLiF4: Er3 , Tm3 , Yb3 , 其中Er3 和Yb3 的浓度保持固定不变, 分别为1 mol%和1.5 mol%, Tm3 浓度变化范围是2 mol%～8 mol%. 在这种共掺杂体系中, 同时观察到了Er3 , Tm3 和Yb3 的吸收, 且Tm3 的吸收随着其浓度的增强而增强. 在980 nm光的激发下, 当Tm3 浓度很小时, 这种材料的上转换发光为白光. 其中蓝光主要来源于Tm3 的激发态1G4到基态3H6的跃迁, 绿光来源于Er3 的4S3/2和2H11/2到基态4I15/2的跃迁, 红光既来源于Tm3 的1G4→3F4的跃迁, 也来源于Er3 的4F9/2→4I15/2的跃迁. 并且这种上转换发光强度随着Tm3 浓度的增强而降低, 但对应不同能级跃迁的发光强度降低的幅度不同, 这是因为Er3 和Tm3 之间的相互作用.     

Tm and Tm-Tb-doped germanate glasses for S-band amplifiers

The mechanism involved in the Tm³⁺(³F₄)→Tb³⁺(⁷F_0,1,2) energy transfer as a function of the Tb concentration was investigated in Tm:Tb-doped germanate (GLKZ) glass. The experimental transfer rate was determined from the best fit of the ³F₄ luminescence decay due to the Tm→Tb energy transfer using the Burshtein model. The result showed that the 1700 nm emission from ³F₄ can be completely quenched by 0.8 mol% of Tb³⁺. As a consequence, the ⁷F₃ state of Tb³⁺ interacts with the ³H₄ upper excited state of Tm³⁺ slighting decreasing its population. The effective amplification coefficient β(cm⁻¹) that depends on the population density difference Δn=n(³H₄)-n(³F₄) involved in the optical transition of Tm³⁺ (S-band) was calculated by solving the rate equations of the system for continuous pumping with laser at 792 nm, using the Runge-Kutta numerical method including terms of fourth order. The population density inversion Δn as a function of Tb³⁺ concentration was calculated by computational simulation for three pumping intensities, 0.2, 2.2 and 4.4 kWcm⁻². These calculations were performed using the experimental Tm→Tb transfer rates and the optical constants of the Tm (0.1 mol%) system. It was demonstrated that 0.2 mol% of Tb³⁺ propitiates best population density inversion of Tm³⁺ maximizing the amplification coefficient of Tm-doped (0.1 mol%) GLKZ glass when operating as laser intensity amplification at 1.47 μm.     

Spectra and lasing properties of Er~(3+),Yb~(3+):phosphate glasses

The effects of Al_2O_3, Yb_2O_3, Er_2O_3 and OH~- on spectral properties of P_2O_5.Na_2O.SrO.Al_2O_3.Yb_2O_3.Er_2O_3 erbium phosphate glass were studied. 5, 8, and 13 mol% Al_2O_3, 4, 5, 6, 7 and 8 mol% Yb_2O_3 and0.05, 0.2, and 0.4 mol% Er_2O_3 were used. It was found that Al_2O_3 can improve fluorescent lifetime ofEr~(3+)ions, but the integrated absorption cross section of Er~(3+)ions decreases with the increase of Al_2O_3concentration. Evaluating from energy transfer efficiency of Yb~(3+)to Er~(3+)and spectral parameters ofYb~(3+)and Er~(3+),we conclude that 6 mol% Yb_2O_3 and 0.4 mol% Er_2O_3 are needed for LD pumped     

Spectroscopic and lasing properties of Er3+:Yb3+-doped fluoride phosphate glasses

Er³⁺ emission and lasing properties at 1.5 μm were studied in fluoride phosphate glasses (FP20) with different doping concentrations as well as in a commercial phosphate glass (Kigre QX). Emission decay behaviour at 1 μm and 1.5 μm was examined with respect to energy transfer between ytterbium and erbium. Emission cross-sections were determined using the reciprocity and Füchtbauer–Ladenburg methods. Gain spectra were calculated for the glasses and related to differences in the tuning curves and lasing properties. The temperature rise due to the quantum defect was determined via the ratios of green upconversion luminescence for different pump powers. The results from the laser and tuning experiments indicate that the FP20 glass offers good possibilities in broadband amplification and the generation of ultrashort pulses. Received: 24 August 2000 / Revised version: 27 October 2000 / Published online: 7 February 2001     

Excitation energy transfer between Er3+ and Tm3+ in LiNbO3

Conclusions Nonradiative energy transfer between similar and different rare-earth ions in LiNbO₃ has been evidenced for the first time. The contribution of nonradiative energy transfer to the decay of the¹G₄ and³H₄ levels of thulium and the⁴S_3/2 and⁴I_13/2 levels of erbium is significant for activator concentrations of the order of several thousand ppm in LiNbO₃. The excitation of higher-lying levels of both activators is transferred faster in codoped crystal to the lowest luminescent levels, from which the luminescence in the 1–2-μm spectral region occurs. This accelerated relaxation is advantageous for broadband optical pumping since the contribution of radiative transitions competing with the³F₄−³H₆ laser transition of thulium is reduced. On the other hand, it appears that erbium ions will influence adversely the efficiency of a laser-diode-pumped LiNbO₃∶Er, Tm laser operating near 1.8 μm since the part of the³H₄ excitation transferred to erbium ions is emitted from the long-lived⁴I_11/2 level of Er³⁺. Furthermore, the⁴I_13/2 excitation is not transferred fully to thulium ions and is lost in⁴I_13/2−⁴I_15/2 emission. Lithium niobate singly doped with thulium is more promising since the cross-relaxation process that transfers the excitation from the³H₄ level to the³F₄ level appears to be efficient in this host. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 125–133, September–October, 1995.     

Er3+及Er3+/Yb3+共掺铋酸盐玻璃光谱性质研究

制备了Ed3+及Ed3+/Yb3+共掺铋酸盐玻璃,测试了样品的吸收光谱、荧光光谱.应用Judd-Oflet理论计算了Er3+在铋酸盐玻璃中的光谱强度参数,分别为Ω2=(5.47-2.92)×10-20cm2,Ω4=(2.16-1.22)×10-20cm2,Ω6=(1.29-0.80)×10-20cm2.比较了Er3+及Er3+/Yb3+共掺铋酸盐玻璃在980 nm附近的吸收截面和1.5μm的荧光发射光谱强度,Er3+/Yba+共掺铋酸盐玻璃的荧光光谱半高宽达到91 nm,比Er3+单掺铋酸盐玻璃大15 nm.用McCumber理论计算了Ed3+在1.5 μm的受激发射截面σe=1.00×10-20cm2.比较了Ed3+在不同基质中的光谱特性,结果表明铋酸盐玻璃更适合作为掺铒光纤放大器的基质材料.     

Enhancement of second-order optical susceptibilities of Er doped germanate glasses

During bicolor optical treatment by two coherent laser beams from 25 ps Erbium-glass laser (λ = 1.54 μm), we have established substantial increase of effective optical second-order susceptibility near the critical temperature points corresponding to the glass structural transformation near 435 °C. The increasing Er³⁺ content favors substantial increase of the photoinduced optical second harmonic generation (SHG). This temperature dependence of the second-order optical susceptibilities detected by the SHG correlates well with the differential scanning calorimetric (DSC) measurements. At the same time, the effect exists only in a narrow temperature range (up to 12 °C) . There was not temperature hysteresis. Possible physical mechanisms of the phenomenon observed are discussed.     

NIR luminescence from Er/Yb, Tm/Yb, Er/Tm and Nd ions-doped zincborotellurite glasses for optical amplification

In this paper, we report the near-infrared luminescence from the Er³⁺/Yb³⁺, Tm³⁺/Yb³⁺, Er³⁺/Tm³⁺ and Nd³⁺ ions-doped TeO₂-ZnO-B₂O₃-Li₂O-Na₂O glasses for optical amplification. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) profiles of the host glass matrix have been carried out. From the DSC thermogram, glass transition (T_g), crystallization (T_c) and melting (T_m) temperatures have been evaluated. The near-infrared spectra of Er³⁺/Yb³⁺, Tm³⁺/Yb³⁺, Er³⁺/Tm³⁺ and Nd³⁺ ions-doped glasses have shown full-width at half-maxima (FWHM) around 58, 127, 87 and 35 nm, respectively. These glasses with better thermal stability and broad near-infrared emissions should have potential applications in broadly tunable laser sources and broadband optical amplification at low-loss telecommunication windows.     

Cr3+,Yb3+,Er3+共掺磷酸盐铒玻璃转镜调Q激光性质研究

研究了Cr3+,Yb3+,Er3+共掺磷酸盐铒玻璃转镜调Q激光性质.三种Er2O3掺杂浓度的激光实验结果表明,在Er2O3名义掺杂浓度为0.5wt%时,玻璃的综合激光性质最好,重复频率为0.1Hz时,它的激光阈值功率为14.5mJ,最大输出能量为9.6mJ,斜率效率为0.55%.在同种实验条件下,比较了Cr14和Kigre公司生产的QE-7S激光性质参数,实验表明,前者激光阈值功率稍低,而后者的斜率效率和最大输出功率略高.     

Broadband near-infrared emission in Er3+-Tm3+ codoped chalcohalide glasses

The near-IR emission spectra of Er3+-Tm3+ codoped 70GeS2-20In2S3-10CsI chalcohalide glasses were studied with an 808 nm laser as an excitation source. A broad emission extending from 1.35 to 1.7 microm with a FWHM of approximately 160 nm was recorded in a 0.1 mol.% Er2S3, 0.5 mol.% Tm2S3 codoped chalcohalide glass. The fluorescence decay curves of glasses were measured by monitoring the emissions of Tm3+ at 1460 nm and Er3+ at 1540 nm, and the lifetimes were obtained from the first-order exponential fit. The luminescence mechanism and the possible energy-transfer processes are discussed with respect to the energy-level diagram of Er3+ and Tm3+ ions.     

Tm3+和Er3+共掺杂氟氧化物玻璃陶瓷材料结构和上转换发光性质的研究

报道了一种新的上转换氟氧化物玻璃陶瓷材料,组份为65GeO2-25NaF-10BaF2(MFG)。研究了Tm^3 和Er^3 共掺MFG玻璃陶瓷中的发光性质。通过X射线衍射和Raman散射分析了MFG玻璃陶瓷的结构性质。分别测量了Tm^3 和Er^3 共掺MFG玻璃及玻璃陶瓷和Er^3 单掺MFG玻璃中的红外发射谱（λex=488nm)和上转换发射谱（λex=978nm)。给出了稀土离子掺入微晶的证据;（1）和MFG：1mol%Tm^3 、2mol%Er^3 玻璃相比,在978nmLD激发下,MFG：1mol%Tm^3 、2mol%Er^3玻璃陶瓷中红色上转换发光大大增强,红不与绿光的比值大大提高。（2）在488nm激光激发下,玻璃陶瓷样品中Tm^3 离子1．7μm左右的发射光谱明显窄化。最后讨论了玻璃陶瓷这种结构上转换发光的影响和其在上转换发光及光通信中的应用潜力。     

Exchange-mediated spin-lattice relaxation of Fe3+ ions in borate glasses

Spin-lattice relaxation times (T1) of two borate glasses doped with different concentrations of Fe2O3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2-6K. In comparison with a previous investigation of Fe3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10-250K range but measured using the amplitude-modulation technique. The T1 values were found to depend on temperature (T) as T(n) with n approximately 1 for the 1% and 0.1% Fe2O3-doped glass samples. These results are consistent with spin-lattice relaxation as effected by exchange interaction of a Fe3+ spin exchange-coupled to another Fe3+ spin in an amorphous material.     

Er3+:GdVO4中Er3+离子的光谱参数计算和晶场中能级分裂的讨论

对Er3+:GdVO4样品的光谱参数以及Er3+在晶场中能级的分裂情况进行了研究.首先对样品进行了吸收光谱的测量,接着用Judd-Ofelt理论拟合出了Er3+在GdVO4晶体中的强度参量Ωt,并由此计算了跃迁的振子强度、自发辐射跃迁速率、荧光分支比和积分发射截面.通过计算结果可以发现有较多能级之间的跃迁都有大于10-6的振子强度和大于10-18 cm的积分发射截面,并且具有较高的荧光分支比,特别是2H11/2→4I15/2,4S3/2→4I15/2,4F9/2→4I15/2和4I13/2→4I15/2等几个强发光能级除了具有较大的振子强度和积分发射截面外还有很好的应用前景,因此也更加值得关注.最后还利用群论讨论了Er3+离子在GdVO4晶场中各能级的分裂情况并对各Stark子能级的Jz混杂情况进行了分析.     

二价碱土金属氟化物对Er3+/Tm3+/Yb3+共掺氟氧锗酸盐玻璃热稳定性和光谱特性影响的研究

制备了分别含有MgF2,CaF2,SrF2或BaF2的Er3+/Tm3+/Yb3+共掺氟氧锗酸盐玻璃试样和包含BaF2纳米晶的玻璃陶瓷试样,所制备试样均具有良好的透光性。对试样的热稳定性和上转换发光特性进行了研究。通过分析试样的吸收光谱发现,随着所含二价阳离子原子量的增大,试样的紫外吸收截止波长明显向短波方向移动。结果显示:通过改变所含二价碱土金属离子的种类能够对激发光的颜色进行调节,特别值得关注的是Mg2+的影响;结果证实:通过对包含二价碱土金属的玻璃进行微晶化处理或者增加二价碱土金属的含量均能提高上转换发光的强度。     

VUV-UV-visible luminescence of Nd3+, Er3+ and Tm3+ in LiLuF4 single crystal host

An overlook of absorption and luminescence characteristics of Nd³⁺, Er³⁺ and Tm³⁺ centers in LiLuF₄ single crystal is provided. Single crystal doped with the mentioned RE ions were prepared by micro-pulling-down technique in the form of few cm long rods with the diameter of about 2 mm. Excitation and emission spectra and fast decay kinetics in VUV spectral region were measured at SUPERLUMI station at synchrotron DESY, Hamburg and characterization was further completed in UV-visible region at conventional spectrophotometers. Observed absorption and emission peaks are ascribed to the 5d–4f and 4f–4f optical transitions in the doped rare earth ions. Concentration dependence of the decay kinetics is discussed.