用Judd-Ofelt理论计算Nd~(3+)离子在LaMgAl_(11)0_(10)单晶中的光谱参数

本文根据Judd-Ofelt理论,利用LaMgAl_(11)O_(19)单晶中Nd~(3+)离子的7个收光谱支项和~4F_(3/2)→~4I_(9/2,11/2,13/2)的三个荧光带计算了谱线强度,振强度,强度参量Ω_(2,4,6),电偶极子跃迁几率及荧光分支比等光谱参数。     

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.     

钕离子1.3μm波段放大特性和浓度猝灭研究

为了研究Nd3+的摩尔分数对1.3μm处荧光的影响,采用常规的熔融方法制备了钕离子掺杂的0.70TeO2-（0.30-x）WO3-xNd2O3(摩尔分数x为0.001,0.003,0.005,0.007,0.01）玻璃系统,得到了Nd3+ 1.3μm荧光光谱,同时还研究了荧光峰值波长的有效线宽和受激发射截面与Nd3+摩尔分数的关系。根据Dexter能量转移理论计算了Nd3+在碲酸盐玻璃中能量转移参量Cd,d(4F3/2,4I9/2→4I9/2,4F3/2)和Cd,a(4F3/2,4I9/2→4I15/2,4I15/2和4F3/2,4I9/2→4I13/2,4I15/2)值和相应发生浓度猝灭的临界距离Rd,d和Rd,a。结果表明,随着Nd3+的掺杂摩尔分数增加,荧光强度也逐渐增加,到0.005时达到最大;随后当Nd3+的摩尔分数大于0.005时,荧光强度逐渐降低。     

Er3 /Yb3 共掺锗碲酸盐玻璃荧光特性及OH-的影响

制备了Er^3 ／Yb^3 共掺的70TeO2-5LiO2(25-x)B2O3-xGeO2(x=0，5，10，15，20％(mol))系列锗碲酸盐玻璃，测试了其荧光光谱、红外吸收谱以及Er^3 的I13/2能级寿命，并根据McCumber理论计算了E^3 能级中^4I13/2→^4I15/2跃迁的受激发射截面。讨论了OH对此系列玻璃荧光特性的影响。结果表明：此系列玻璃作为掺Er^3 光纤放大器(EDFA)的基质材料具有较好的带宽特性，随着GeO2含量的增加及B2O3含量的减少，Er^3 的荧光强度和^4I13/2能级寿命逐渐提高，OH^-的存在使得Er^3 的荧光强度降低，荧光寿命减小。     

γ射线辐照对Cr掺杂MgAl2O4晶体光谱特征的影响

为评估辐照对Cr:MgAl₂O₄晶体光谱特性的影响,采用辐照剂量为100 Mrad的⁶⁰Co γ射线照射抛光后的Cr:MgAl₂O₄晶体样品片,测量了辐照前后的拉曼光谱、透射光谱和荧光特性,并对辐照前后光谱变化的原因进行了分析。研究结果表明:样品的拉曼振动峰值的位置和强度都受到辐照的影响,但振动峰的数量没有改变;由于色心的吸收,辐照后250～600 nm波长范围内的透射率均明显降低;辐照前后样品的荧光发射峰位一致,但辐照后荧光强度明显降低,同时辐照后的荧光寿命显著增加。     

高浓度铒离子掺杂钨酸镱钾激光晶体上转换发光研究(英文)

首次采用泡生法生长了掺铒钨酸镱钾(分子式:Er3+:KYb(WO4)2,简称:Er:KYbW)激光晶体。室温下测试了该晶体的吸收及上转换发射光谱。在荧光光谱中,观察到3个较为明显的上转换发射带,分别位于470~560nm,645~675 nm,750~850 nm。其中,位于533 nm处的上转换绿光强度最大。基于能量匹配原理分析了晶体上转换发光基质,结果表明,上转换红光和绿光的发光渠道均为双光子过程。根据J-O理论,计算了光谱参数,强度参数为:Ω2=16.342×10-20cm2,Ω4=4.183×10-20cm2,Ω6=1.264×10-20cm2;对应于绿光4S3/2-4I15/2跃迁的荧光分支比为76.37%,荧光寿命为278μs。这些光学参数表明Er:KYbW激光晶体可实现高效上转换绿光发射。     

NdP_5O_(14)的光谱和能级

本文报导测定水热法生长的激光晶体NdP_5O_(14)和Nd_xLa_(1-x)P_5O_(14)的光谱特性。从所测结果得知,改变Nd_xLa_(1-x)P_5O_(14)晶体中组分x,对峰值位置没有影响。由吸收光谱计算了主要吸收峰的吸收截面和振子强度。红外光谱测试结果表明,我们生长的NdP_5O_(14)晶体中不含有OH和P-OH键。测定了晶体的荧光光谱,在改进实验装置的情况下,测出了荧光强度较弱的4~F_(3/2)→4~I_(13/2)跃迁。根据所测光谱数据,确定了NdP_5O_(14)晶体中Nd~(3 )离子室温实验能级。所得结果与文献报导相符。     

掺Er~(3+)碲硼酸盐玻璃1.53μm波段荧光强度提高研究

用高温熔融法制备了系列70TeO2-(25-x)B2O3-xGeO2-5Na2O(x=5,10,15和20 mol%)掺Er3+碲硼酸盐玻璃。为提高1.53μm波段的荧光发射强度,测试了玻璃样品的吸收光谱、红外透射谱、1.53μm波段荧光谱及4I13/2能级Er3+荧光寿命,结合Judd-Ofelt(J-O)理论分析了Er3+光谱特性随玻璃组分含量的变化,进而研究了玻璃中OH基对1.53μm波段荧光强度的影响。结果表明,碲硼酸盐玻璃具有较好的宽带荧光谱特性,其有效带宽大于72 nm;随着玻璃中GeO2逐步替代B2O3,1.53μm波段荧光强度相应提高。同时,通过O2鼓泡除水处理,能减少玻璃中OH基含量并减弱4I13/2能级上Er3+到OH基的无辐射能量传递,从而进一步提高了Er3+荧光寿命和1.53μm波段荧光强度。     

Er3+/Yb3+共掺锗碲酸盐玻璃的热稳定性、 Judd-Ofelt理论分析和光谱性质

用高温熔融法制备了一种Er3 /Yb3 共掺的70TeO2-5Li2O-10B2O3-15GeO2玻璃.测试和分析了其热稳定性、吸收光谱、荧光光谱和上转换发光.应用Judd-Ofelt理论计算了玻璃中Er3 的强度参数、自发辐射跃迁几率、辐射寿命以及荧光分支比.结果表明:这种玻璃具有较好的热稳定性,较宽的荧光半高宽和较大的受激发射截面,位于532 nm、546 nm和659 nm的上转换绿光和红光,分别对应于Er3 离子2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2的辐射跃迁,是一种较为合适的宽带光纤放大器和上转换激光器的基质材料.     

~4F_(3/2)→~4I_(11/2)和~4F_(3/2)→~4I_(13/2)跃迁的掺Nd~(3 )铍酸镧晶体的生长、光谱和激光性能

在77K和300K下对a、b、c三个结晶取向La_2Be_2O_5晶体中Nd~(3 )的~4F_(3/2)→~4I_(11/2)主跃迁和~4F_(3/2)→~4I_(13/2)次跃迁多重态间荧光强度各向异性进行了详细研究。对~4F_(3/2)→~4I_(11/2,13/2)频道测定了主光谱特性的取向值,包括斯塔克荧光分支比β_(ij)~(or),跃迁峰值和有效截面(σ_(e、ij)~(or)和σ_e~(off))以及在此跃迁波长下激发的受激发射。在77～300K温度范围内,对~4F_(3/2)→~4I_(11/2)跃迁频道研究了(F‖C) La_2Be_2O_5:Nd~(3 )晶体激光谱线的温度特性。在液氮温度范围内观察到了1.0694和1.0785微米激光谱线的再转换。根据光谱研究解释了这种效应。重新找到La_2Be_2O_5晶体中Nd~(3 )离子的斯塔克能级的能量并核对了所有激发激光谱线。对La_2Be_2O_5中Pr~(3 )离子的光谱性能进行了初步分析,并确定了多重态晶场分裂图,其能级间的跃迁符合La_2Be_2O_5晶体的光学透明带。     

Photo-induced magnetism in La0.5Pr0.5CrO3

In a perovskite-type chromite La_0.5Pr_0.5CrO₃, we studied the photo-induced electron-spin resonance (ESR). During the illumination of near-infrared light, the photo-induced and transient magnetization is temperature dependent with the characteristic thermal activation energy of 130 meV below the spin-canted antiferromagnetic transition temperature 261 K. At room temperature the photo-induced ESR intensity is remarkably enhanced. We interpret this is coming from the photo-excited electronic state in chromite. By analogy with the manganites, we suspect that the irradiated photons excite the t_2g electrons to the e_g state in Cr³⁺ (3d³). This kind of excitation may cause a creation of novel transient magnetic order than canted antiferromagnetism. The present results may open up an intriguing collective photo-induced magnetism, the creation and control of spin and spin-polarization dependent transport with near-infrared light illumination.     

Red to blue upconversion luminescence in Tm doped ZrF4-ZnF2-AlF3-BaF2-YF3 optical glass

We report on the preparation and optical spectroscopy analysis of a new fluoride glass in the chemical composition of 20ZrF₄-30ZnF₂-25AlF₃-10BaF₂-15YF₃ with Tm³⁺ as the luminescent ions. Under an UV source, this material has displayed an intense blue emission colour. Upon excitation with a red wavelength at 688 nm (³H₆→³F₃), this glass has shown two upconverted blue emissions at 452 nm (¹D₂→³F₄) and 474 nm (¹G₄→³H₆), respectively. Possible mechanisms involved in such upconverted blue emissions are explained via ground state absorption and excited state absorption processes through an energy-level structure diagram of Tm³⁺(4f¹²). By the successful application of Judd-Ofelt calculations, the luminescence results have successfully been analysed. Besides obtaining a clear understanding of the optical characteristics of this glass, we have also measured its physical properties such as the refractive indices at three different wavelengths in order to evaluate its light dispersion performance, glass density and other related parameters as well.     

Sm3+掺杂(Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3高熵粉体的制备及其荧光性能研究

采用固相法制备了稀土Sm³⁺(0～0.10 mol)掺杂的(Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃高熵荧光粉。研究发现,随着Sm³⁺掺杂量的增加,(Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃高熵粉体逐渐出现了Sm₂Ti₂O₇杂相,其发光强度发生明显变化。当Sm³⁺掺杂量为0.04 mol时,(Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃高熵粉体具有单一的钙钛矿结构,且各元素组分分布均匀,并表现出最佳的荧光性能。当...     

High quality silicon nitride deposited by Ar/N2/H2/SiH4 high-density and low energy plasma at low temperature

The high-quality PECVD silicon nitride has been deposited by high-density and low-ion-energy plasma at 400 °C and the effect of the process parameters, such as silane and nitrogen flow rate, pressure, on its structure and electrical properties has been investigated. The experimental results show that silane flow rate is the most sensitive parameter for determining deposition rate and N/Si atomic ratio of silicon nitride in the range of process parameters employed. The change of nitrogen flow rate leaded to slightly change in deposition rate, however, it effects significantly on the refractive index or densification of silicon nitride. With the addition of hydrogen gas in plasma, the hysteresis of C-V characteristics of MIS structure decreases from 0.4 to 0.1 V. The moderate increment of ion energy makes further reduction in the hysteresis of C-V characteristics of MIS from 0.1 V to below 0.05 V. The interface trap density of 6.2×10¹⁰ (ev⁻¹ cm^-2), deduced from the high frequency and quasistatic C-V characteristics of the MIS structure, is about the same as that of LPECVD silicon nitride deposited at the range of 750-850 °C. The stoichiometric silicon nitride of excellence electric and structural properties is obtained by Ar/N₂/H₂/SiH₄ high-density and low ion energy plasma.     

Microstructure and electrical characteristics of Ba0.65Sr0.35TiO3 thin films etched in CF4/Ar/O2 plasma

Radio frequency magnetron sputtered Ba_0.65Sr_0.35TiO₃ (BST) thin films were etched in CF₄/Ar/O₂ plasma by magnetically enhanced reactive ion etching technique. The etching characteristics of BST films were characterized in terms of microstructure and electrical properties. Atomic force microscopy and X-ray diffraction results indicate that the microstructure of the etched BST film is degraded because of the rugged surface and lowered intensities of BST (1 0 0), (1 1 0), (1 1 1) and (2 0 0) peaks compared to the unetched counterparts. Dielectric constant and dielectric dissipation of the unetched, etched and postannealed-after-etched BST film capacitors are 419, 346, 371, 0.018, 0.039 and 0.031 at 100 kHz, respectively. The corresponding dielectric tunability, figure of merit and remnant polarization are 19.57%, 11.56%, 17.25%, 10.87, 2.96, 5.56, 3.62 μC/cm², 2.32 and 2.81 μC/cm² at 25 V, respectively. The leakage current density of 1.75 × 10⁻⁴ A/cm² at 15 V for the etched BST capacitor is over two orders of magnitude higher than 1.28 × 10⁻⁶ A/cm² for the unetched capacitor, while leakage current density of the postannealed-after-etched capacitor decreases slightly. It means that the electrical properties of the etched BST film are deteriorated due to the CF₄/Ar/O₂ plasma-induced damage. Furthermore, the damage is alleviated, and the degraded microstructure and electrical properties are partially recovered after the etched BST film is postannealed at 923 K for 20 min under a flowing O₂ ambience.     

pH, pK and pNa detection properties of SiO2/Si3N4 ISFET chemical sensors

This article reports the technological fabrication and the electrical characterisation of SiO₂/Si₃N₄ ion sensitive field effect transistors (ISFET) for the detection of H⁺, K⁺ and Na⁺ ions. ISFET chemical sensors show quasi-nernstian pH response with sensitivities around 54 mV/pH. pK and pNa measurements are also investigated, evidencing sensitivities lower than 20 mV/pH and non-nernstian pH-dependent phenomena for the highest K⁺ or Na⁺ concentrations (pK and pNa, respectively, lower than 4 and 3). It is shown that the detection properties of H⁺, K⁺ and Na⁺ ions are dependent on each other, being responsible for saturation effects for the highest concentrations. It is finally concluded that SiO₂/Si₃N₄ ISFETs are well adapted for the pH measurement, can be used for the pK or pNa measurements in the case of buffered solutions but are not fully suitable for multi-ion detection in the case of medical analysis.     

Fluorescence enhancement of single-phase red-blue emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors via Dy3+ addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺ phosphors for plant cultivation has been investigated by Dy³⁺ addition. The Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺,Dy³⁺(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy³⁺ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation. This work has been supported by National Natural Science Foundation of China (Grant No 50872091) and the Natural Science Foundation of Tianjin, China (06YFJMJC02300, 06TXTJJC14602).     

Effect of strontium nitride on the properties of Sr2Si5N8：Eu2＋ red phosphor

The nitride phosphor Sr₂Si₅N₈:Eu²⁺ was synthesized by the high temperature solid-state method. The properties of Sr₂Si₅N₈:Eu²⁺ were discussed by X-ray diffraction (XRD) scanning electron microscope (SEM) and spectra analysis. The XRD pattern shows that the single phase produces when strontium nitride is a bit excessive. The SEM photo implies that the excessive strontium nitride works as a flux in the reaction system. The position of emission peak is also located at about 612 nm as strontium nitride is excessive. The luminescent intensity of the phosphor adding excessive strontium nitride is higher than that of the phosphor introducing stoichiometric strontium nitride. The optimized content of nitride strontium was 2.05 mol/mol for the obtained phosphor with excellent properties.     

Concentration-dependent luminescence properties in Er3+-doped TeO2-ZnO-La2O3 glasses

Erbium-doped tellurite-based glasses(Er3+:TeO2-ZnO-La2O3) are prepared by the conventional melt-quenching technique,and concentration-dependent luminescence properties of Er3+ are investigated.A significant spectral broadening of the 1.53 μm fluorescence corresponding to 4I13/2 →4I15/2 transition is observed,and the fluorescence decaying becomes a nearly exponential way with the increasing Er3+concentration.Radiation trapping is evoked to explain the broadening of 4I13/2 → 4I15/2 emission line of Er3+ ions.The optimum doping content of Er2O3 for 1.53 μm fluorescence emission is about 1.5 mol%.