掺铒碲酸盐玻璃的热力学稳定性和光谱性质的研究

分析了掺Er³⁺碲酸盐玻璃的热力学稳定性能,研究了掺Er3+碲酸盐玻璃的吸收和荧光光谱性质;应用Judd-Ofelt理论计算了碲酸盐玻璃中Er3+离子的强度参数Ω(Ω₂=4.79×10^-20cm², Ω₄=1.52×10^-20cm²,Ω₆=0.66×10^-20_cm2),计算了离子的自发跃迁几率,荧光分支比;应用McCumber理论计算了Er3+的受激发射截面(σ_e=10.40×10^-21cm²)、Er³⁺离子⁴I_13/2→⁴I_15/2 发射谱的荧光半高宽(FWHM=65.5nm)及各能级的荧光寿命(⁴I_13/2能级为τ_rad=3.99ms);比较了不同基质玻璃中Er3+离子的光谱特性,结果表明掺铒碲酸盐玻璃更适合于掺Er³⁺光纤放大器实现宽带和高增益放大.     

1.3 μm Emission from Nd3+-doped Tellurite Glass Fiber

1 wt pct Nd2O3-doped tellurite bulk glass and fiber with the same composition of 75TeO2-15ZnO-5Na2O-5Li2O (molfraction, %) were fabricated. Judd-Ofelt analysis was carried out for the bulk. The emission from the 4F3/2→4I13/2 transition in fiber is at 1.33 μm wavelength with a spectral bandwidth of 55 nm, which is similar to that in bulk. In the case of the fiber, the lifetime of 4F3/2 level is 164μs, and the quantum efficiency is ～100%. The figure-of-merit for gain (σoT0) for Nd3 -doped tellurite glass is about 2.8×10-24 cm2.s, which is quite comparable with that in Nd3 -doped fluoroaluminate glasses, and is an order of magnitude larger than pr3 -doped fluoride glasses.     

利用窄得-奥菲特理论研究Tm:Lu2SiO5晶体的光谱特性

采用丘克拉斯基(Czochralski)技术生长了掺铥硅酸镥(Tm∶Lu2SiO5,Tm∶LSO)晶体;测量了LSO晶体在室温下的非偏振吸收光谱和非偏振荧光光谱;利用窄得-奥菲特(Judd-Ofelt)理论计算了Tm∶LSO晶体的窄得-奥菲特强度参数、振子强度、自发辐射概率、辐射寿命、积分吸收截面和积分发射截面.Tm∶LSO晶体的强度参数为Ω2=9.1355×10-20cm2,Ω4=8.4103×10-20cm2,Ω6=1.5908×10-20cm2;Tm∶LSO晶体在1.9μm附近有明显的发射峰(3F4→3H6跃迁),相应的辐射寿命为2.03 ms,积分发射截面为5.81×10-18cm2,半峰全宽(FWHM)为250 nm.用Tm∶LSO晶体在77 K温度下实现了激光运转.利用792 nm的激光二极管(LD)作为抽运源,获得中心波长为1960 nm的激光输出,抽运阈值为2.13 kW/cm2.     

Er3 /Yb3 共掺TeO2-WO3-Bi2O3玻璃的光谱性质

用高温熔融法制备了Er3+/Yb3+共掺的TeO2-WO3-Bi2O3玻璃,研究了该玻璃的吸收和荧光光谱性质.应用Judd-Ofelt(JO)理论计算了Er3+的谱线强度、自发辐射跃迁几率、荧光分支比和辐射寿命等光谱参数,并拟合了相应的强度参数Ωt(t＝2,4,6).Er3+在该玻璃中4I13/2→4I15/2发射的荧光半高宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面为1.03×10-20cm2.其带宽特性FWHM×σpeake乘积优于掺Er3+的硅酸盐、磷酸盐和铋酸盐玻璃,说明这是一种制备宽带光纤放大器的优良基质材料.Er3+在400～850nm波长范围存在着5个上转换发射峰,分别对应Er3+的激发态4I7/2、2H11/2、4S3/2、4F9/2和4I9/2到基态4I15/2的发射,分析了其可能存在的上转换过程.     

Investigation of luminescence and spectroscopic properties of Nd3+ions in cadmium alkali borate glasses

Neodymium doped cadmium alkali borate glasses having composition 20CdO20R₂O59.5H₃BO₃0.5Nd₂O₃; (R = Li, Na and K) were prepared by conventional melt-quenching technique. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The physical properties such as density, refractive index, molar volume, rare earth ion concentration etc. were determined. Optical absorption and fluorescence spectra were recorded. The Judd-Ofelt theory was applied on the optical absorption spectra of the glasses to evaluate the three phenomenological intensity parameters Ω₂, Ω₄ and Ω₆. These parameters were in turn used to predict the radiative properties such as the radiative transition probability (A), radiative lifetime (τ_R) and branching ratio (β_R) for the fluorescent levels of Nd³⁺ ion in the present glass series. The lasing efficiency of the prepared glasses has been characterized by the spectroscopic quality factor (Ω₄/Ω₆), the value of which is in the range of 0.2–1.5, typical for Nd³⁺ in different laser hosts. The variation of Ω₂ with the change in alkali oxide has been attributed to the changes in the asymmetry of the ligand field at the rare earth ion site. The shift of the hypersensitive bands, study of the oscillator strengths and the variation of the spectral profile of the transition ⁴I_9/2 → ⁴F_7/2 + ⁴S_3/2 indicate a maximum covalency of NdO bond for glass with potassium ions. From the fluorescence spectra, peak wavelength (λ_p), effective line widths (Δλ_eff) and stimulated emission cross-section (σ_p) have been obtained for the three transitions ⁴F_3/2 → ⁴I_9/2, ⁴F_3/2 → ⁴I_{11/2 and} ⁴F_3/2 → ⁴I_13/2 of Nd³⁺ ion. The relatively high values of σ_p obtained for Nd³⁺ in present glass system suggest that these materials can be considered as suitable candidates for laser applications. The glass with potassium ions shows the highest value of the stimulated emission cross-section.     

Er:GSGG 晶体的光谱性质分析及激光特性模拟研究

测试和分析了Er:GSGG的吸收光谱和荧光光谱。应用Judd-Ofelt理论计算了Er3+的强度参数、自发辐射跃迁几率、能级寿命、荧光分支比和吸收截面。结果表明,Er3+在4I13/2和4I11/2能级有较长的能级寿命,在966nm和790nm处有较大的吸收截面,在2.79µm处有较大的积分发射截面值,数值模拟了在966nm泵浦下激光输出特性,在泵浦速率达到一定值时,有较高的量子效率。结果表明Er:GSGG有望成为2.79µm波段的理想激光晶体。     

掺Er3+碲锌铋酸盐玻璃光谱特性研究

制备了掺铒碲锌铋酸盐玻璃样品84.5TeO2-(15-x)ZnO-xBi2O3-0.5mol% Er2O3(TZB x=0,2,4,6,8,10mol%).测试和分析了玻璃样品的吸收光谱、荧光光谱和4I13/2能级寿命等参数.根据McCumber理论,计算了Er3 受激发射截面(σpeake=(6.31～8.57)×10-21cm2)、并测量了Er3 荧光半高度(FWHM=65～70nm).结果表明:适量Bi2O3(～6mol%)的引入,能较好地改善玻璃样品FWHM,σpeake,4I13/2能级寿命和量子效率等光谱参数.     

Enhanced luminescence properties of Eu3+ in La2MoO6 by nonsensitization of Bi3+

It was unusual for Bi³⁺ ions to enhance the emission intensity of phosphors via nonsensitization. Here, La₂MoO₆:Eu³⁺, Bi³⁺ phosphors were successfully synthesized by a high temperature solid-state reaction method in air atmosphere. As the increase of doping concentration of Bi³⁺, the emission spectra of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors had obvious shifts, splits and the enhancement of intensities, which indicated that the characteristics of the phosphors were modified. To analyze these phenomena, the crystal structure refinements, spectral characteristic analyze and Judd-Ofelt theoretical calculation were mainly performed. Bi³⁺ ions played the role of the nonsensitizer and affected the distortion of the crystal, the sites of Eu³⁺ ions, the field splitting energy and the internal quantum yield. Moreover the nephelauxetic effects of Bi³⁺ ions and the ET process caused synergistically the life times of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors to increase and then gradually decrease. The CIE coordinates of phosphors changed within a small range. This study might be instrumental in promoting the further application of Bi³⁺ ions in rare earth luminescent materials.     

Upconversion Emission in Er^3＋ Doped Novel Bismuthate Glass

Novel Er3 -doped bismuth lead strontiam glass was fabricated and characterized, and the absorption spectrum and upconversion spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were found to be Ω2＝3.27×10-20 cm2, Ω4＝1.15×10-20 cm2, and Ω6＝0.38×10-20 cm2. The oscillator strength, the spontaneous transition probabilities, the fluorescence branching ratios, and excited state lifetimes were also measured and calculated. The upconversion emission intensity varies with the power of infrared excitation intensity. A plot of log Iup vs log IIR yields a straight line with slope 1.86, 1.88 and 1.85, corresponding to 525, 546, and 657 nm emission bands, respectively, which indicates that a two-photon process for the red and green emission.     

White emitting Dy3+ activated perovskite titanates and energy transfer by Eu3+ codoping

Perovskite type titanate phosphors Sr_0.97−xDy_0.03Li_xTi_1−xNb_xO₃, Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ and Sr_0.87−yDy_0.03Eu_yLi_0.1Ti_0.9Nb_0.1O₃ were prepared by conventional solid state method. Herein, white light emission from Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ phosphors and the lowering of its color temperature through codoping with Eu³⁺ ions are reported. Raman measurements have shown that the incorporation of dopants alters the vibrational properties of these phosphors significantly, indicating the reduction of the local symmetry in the crystal lattice. The addition of LiNbO₃ in SrTiO₃:Dy³⁺ phosphor enhances the luminescence intensity and the yellow to blue ratio resulting in emission of high quality white light with color coordinates corresponding to that of standard white. Life time measurements and data fits of Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ phosphors revealed the biexponential behaviour of luminescence decay profiles. From Judd-Ofelt analysis it is found that the intensity parameter Ω₂ increases with Dy³⁺ concentration and a quantum efficiency of 90.4% was obtained for optimum concentration. In the case of Dy³⁺ and Eu³⁺ codoped phosphors, the color coordinates are found to be sensitive to the Eu³⁺ concentration and the highest energy transfer efficiency of 92% was obtained for the phosphor doped with 10 mol% Eu³⁺. The emission color changes from cold white to reddish orange when the wavelength of excitation alters from 452 to 388 nm, since the energy transfer mechanism alone take place under 452 nm excitation and both direct absorption and the energy transfer mechanism occurs under 388 nm excitation.