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1.
Polycrystalline GdAl 3(BO 3) 4 phosphors codoped with Yb 3+/Tb 3+ and/or Nd 3+/Yb 3+/Tb 3+ have been synthesized by combustion method. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence
has been observed in GdAl 3(BO 3) 4:Yb,Tb phosphor. The quadratic dependence of the luminescence on the pump-laser power indicating a cooperative energy transfer
process. Meanwhile, it is noticed that upon excitation with 808 nm laser diode, intense luminescence has clearly been detected
in GdAl 3(BO 3) 4:Nd,Yb,Tb phosphor. The luminescence intensity exhibits also a quadratic dependence on incident pump-laser power. However,
no green-emission has been observed in GdAl 3(BO 3) 4 phosphors codoped with Yb 3+/Tb 3+ or Nd 3+/Tb 3+ respectively upon excited at 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd 3+ to Yb 3+, and then a cooperative energy transfer process from two excited Yb 3+ to Tb 3+ has been presented. 相似文献
2.
Polycrystalline samples of europium-doped K 5Li 2GdF 10 have been obtained by a slow cooling of melted compound and investigated using spectroscopy methods. Luminescence from the
5
D
2 level of Eu 3+ is found to be weak. Intense visible emission upon excitation into the 5
D
2 or higher energy levels has been attributed to overlapping transitions from long-lived 5
D
1 and 5
D
0 levels. A strong increase of the 5
D
0 emission at the expense of the 5
D
1 emission occurs between 5 K and 25 K without significant change of the 5
D
1 lifetime. To account for this, it is supposed that both the radiative and the nonradiative transition rates are temperature-dependent.
Efficient energy transfer from the 6
G
J levels of Gd 3+ to Eu 3+ ions has been evidenced by excitation spectra in the VUV region and VUV-excited luminescence. It has been concluded that
the cross relaxation contributes to the energy-transfer process.
Received: 8 May 2001 / Accepted: 11 May 2001 / Published online: 25 July 2001 相似文献
3.
Fluorescence spectrum of Dy 3+, Dy 3+-Ho 3+, Tb 3+ and Tb 3+-Er 3+ doped in calibo glass have been studied using Ar + and excimer lasers. Non-radiative energy transfer from trivalent dysprosium and terbium (donors) to holmium and erbium (acceptors)
respectively has been observed on the basis of decrease in the life time of the levels and reduction in fluorescence intensity
of Dy 3+ and Tb 3+ on increasing Ho and Er concentrations. The interaction mechanism of donor and acceptor ions is found to be dipole-dipole
in both cases. Various parameters such as donor-acceptor distances, non-radiative energy transfer efficiency ( η) and energy transfer probability ( P
da) have been computed. Stark splitting have also been marked in several intense transition of the two. 相似文献
4.
Conclusions Alkaline silicate glasses seem to be good candidates as host materials for codoping with Cr 3+ and Tm 3+. Cr 3+ ions occupy mainly low-field sites in them, and their broadband emission overlaps Tm 3+ excitation. As a consequence very high efficiency for the energy transfer Cr 3+→Tm 3+ is achieved with moderate concentrations of these ions. Moreover, the average lifetime of the Cr 3+ ions in codoped glasses is long enough to allow significant energy storage by flashlamp pumping.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 115–120, September–October, 1995. 相似文献
5.
本文研究了单掺和双掺(Eu3+,Bi3+,Fu3++Bi3+)约二十余种不同成份的硼酸盐玻璃,探讨了玻璃成份对Eu3+发光性质的影响和Bi3+对Eu3+的敏化作用. 相似文献
6.
Conclusions Nonradiative energy transfer between similar and different rare-earth ions in LiNbO 3 has been evidenced for the first time. The contribution of nonradiative energy transfer to the decay of the 1G 4 and 3H 4 levels of thulium and the 4S 3/2 and 4I 13/2 levels of erbium is significant for activator concentrations of the order of several thousand ppm in LiNbO 3. 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 the 3F 4− 3H 6 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 LiNbO 3∶Er, Tm laser operating near 1.8 μm since the part of the 3H 4 excitation transferred to erbium ions is emitted from the long-lived 4I 11/2 level of Er 3+. Furthermore, the 4I 13/2 excitation is not transferred fully to thulium ions and is lost in 4I 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 the 3H 4 level to the 3F 4 level appears to be efficient in this host.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 125–133, September–October, 1995. 相似文献
7.
本文利用毫微秒技术在ns秒量级测量了不同浓度组分的LaOBr:Ce3+,Tb3+中Ce3+发射带的衰减常数τCe值和时间分辨光谱,确立了Ce3到Tb3+能量传递过程模型,建立了动力学方程和导出能量传递的计算公式。据此计算出Ce3+到Tb3+的能量传递几率和效率,得出Ce3+,Tb3+的最佳浓度。 相似文献
8.
Nd 3+, Sm 3+ and Eu 3+ have been intercalated by cation exchange into CdPS 3. The photoluminescence and IR spectra show the creation of cadmium cation vacancies. Crystal field analysis indicates that the rare earths have entered the intralamellar vacancies and formed a complex defect center with C 2 or lower symmetry. 相似文献
9.
Sensitization of the fluorescence of Er3+ in fluoride phosphate glass containing up to 20 mol% phosphates by codoping with Cr3+ and Yb3+ is shown. The low order of ligand field strength for Cr3+ (Dq/B=2.04) results in broad Cr3+ fluorescence overlapping the Yb3+ absorption. The electronic energy transfer efficiency approaches 100%. Deviations of donor decay from the Förster law are interpreted in terms of the inhomogeneously acceptor distribution. The electronic energy transfer efficiency of Yb3+ → Er3+ reaches a maximum value of 75% for glasses containing 20 mol% phosphates. The transfer is shown to be migrationally accelerated by means of GAF-LAF-FB theory. From Judd-Ofelt parameters a stimulated emission cross-section for the transition4I13/2 →4I15/2 of Er3+ of 6.2×10−20 cm2 is derived. The c.w. laser action of Er3+ by Cr3+ excitation and double-step energy transfer is shown. The output is tuned continuously from 1536 to 1596 nm. Flashlamp pumping is also shown. 相似文献
10.
The energy transfer dynamics between Yb 3+ and Er 3+ ions in lithium niobate is investigated after ytterbium-pulsed excitation at 920 nm. The sensitisation of the LiNbO 3:Er 3+ system with Yb 3+ ions does not modify the lifetime of the 4I 13/2 erbium level (1.5-μm emission), whereas it induces a marked, concentration-dependent change in the lifetime of the 2F 5/2 (Yb 3+) and 4S 3/2 (Er 3+) multiplets (1060-nm and 550-nm emissions, respectively). The results are analysed by using the rate-equation formalism and
cross-relaxation model for the energy transfer.
Received: 15 October 1998 / Revised version: 24 November 1998 / Published online: 24 February 1999 相似文献
11.
Calcium metasilicate phosphors activated by Ce 3+ and Tb 3+ have been studied for their emission characteristics. In two series of phosphors, one activator was kept at its optimum value while the other was varied. In another two series, one activator was kept below its optimum value and the other was varied. Concentration quenching effects start when each activator gives its maximum emission. There is clear evidence of an energy transfer from Ce 3+ to Tb 3+ because the 5 D 3 lines appear on addition of Ce 3+ while they were conspicuously absent when Tb 3+ alone was present. Their absence in singly activated phosphors could not have been due to cross-relaxation. Obviously X-ray excitation does not lead to 5 D 3 transitions which are achieved only by energy transfer. Further, considering the features of the emission spectra and the concentrations of activators used, the transfer could only be of the dipole-dipole type. 相似文献
12.
Bi 3+ and Eu 3+ codoped cubic Gd 2O 3 nanocrystals were prepared by the Pechini sol-gel method. Their photoluminescent properties were investigated under ultraviolet
light excitation. The introduction of Bi 3+ ions broadened the excitation band of Eu 3+ emission, of which a new strong band occurred ranging from 320 to 380 nm due to the 6s 2→6s6p transition of Bi 3+ ions, implying a very efficient energy transfer from Bi 3+ ions to Eu 3+ ions. Upon 325 and 355 nm light excitation, the luminescent intensity of Eu 3+ ions was remarkably improved by the incorporation of Bi 3+ ions. But a significant quenching of Eu 3+ emission was observed under 266 nm light excitation when Bi 3+ was codoped. The possible energy transfer processes between Bi 3+ and Eu 3+ were discussed. The decay curves of Eu 3+ emission under the excitation of 266 nm pulsed laser were measured and gave further evidence for our discussion. 相似文献
13.
The paramagnetic resonance of trivalent Er and Ce in single crystals of Y 2O 3 on sites of crystal field symmetry C 3i and C 2 is investigated at 9.5 kMe/s. For Er 3+ ions completing results to formerly published data are given. For Ce: Y 2O 3 the measured values of the g-tensors are: g ‖=0.394 and g ⊥=1.633 for C 3i -sites and g z =0, g x =2.938, g y =0.819 for C 2-sites. For ions on sites of symmetry C 2 the principal axes x and y of g are tilted 29.7° against the [100] directions. 相似文献
14.
Magnetic field and temperature dependent photon echo behavior in LaF 3:Nd 3+ and YAG:Nd 3+ is reported and compared with corresponding behavior in CaWO 4:Nd 3+. 相似文献
15.
The photoacoustic spectra(PAS) of the coprecipitates Tb 3+-Gd 3+-Sal complexes are reported. With the increase of the concentration of Gd 3+ ion, the PA intensity of complexes decrease firstly, then increase. It is indicated that the addition of the second rare earth ion Gd 3+ changes the relaxation processes of the complexes. The changes of the fluorescence spectra turn out complementary to the PAS. The intramolecular energy transfer and the intermolecular energy transfer processes in coprecipitates are discussed. 相似文献
16.
Tm 3+-Eu 3+ energy transfer processes and relaxation dynamics of the 3
H
4 and 3
F
4 excited states of Tm 3+ ions in 1 at. % Tm 3+, 5 at. % Eu 3+:YVO 4 single crystal were studied. Contribution of Tm 3+-Eu 3+ energy transfer reduces effectively the lifetime of terminal level in a potential 3
H
4– 3
F
4 laser transition at around 1.48 μm. Adverse quenching of the 3
H
4 emission by Eu 3+ ions is found to be less efficient than that reported for Tm 3+ + Tb 3+ system in YVO 4. The classical Inokuti–Hirayama model accounts well for an experimental decay curve of the 3
H
4 emission recorded for co-doped crystal. Stimulated emission cross section for 3
H
4– 3
F
4 transition of Tm 3+ at around 1.48 μm was analyzed taking into account the anisotropy of YVO 4 crystal. PACS 42.55.Xi; 42.62.Fi 相似文献
17.
Results of cooperative phenomena investigations in the impurity subsystem of lithium niobate crystals doped with Er 3+ and co-doped with Yb 3+ impurity ions under continuous wave and pulsed excitation at 975 nm and 1064 nm wavelengths are presented. Dependences of some spectroscopic characteristics on the intensity of laser pumping are studied. Based on the pair centers model the analysis of the cooperative luminescence behavior in LiNbO 3:Yb 3++Er 3+ crystals is performed. 相似文献
18.
Institute of Physics, Czech Academy of Sciences, Cukrovarnicka 10, 16200 Prague 6, Czech Republic. Published in Zhurnal Prikladnoi
Spektroskopii, Vo. 62, No. 5, pp. 71–77, September–October, 1995. 相似文献
19.
The luminescence properties of polyphosphates NaEu x Gd (1?x)(PO 3) 4 ( x = 0–1.00) and the energy transfer from Gd 3+ to Eu 3+ were studied. In undoped NaGd(PO 3) 4 sample, the photon cascade emission of Gd 3+ was observed under 8S 7/2 → 6G J excitation (201 nm) in which the emission of a red photon due to 6G J → 6P J transition is followed by an ultraviolet photon emission due to 6P J → 8S 7/2 transition. When part of Gd 3+ ions in the host NaGd(PO 3) 4 were substituted by Eu 3+ ions, the NaGd(PO 3) 4:Eu 3+ sample showed intensive red emission under 172-nm vacuum-ultraviolet (VUV) excitation which is suitable for mercury-free fluorescent lamps and plasma display panel applications. Based on the VUV–visible spectroscopic characteristics and the luminescence decay properties of NaGd(PO 3) 4:Eu 3+, it was found that the quantum cutting by a two-step energy transfer from Gd 3+ to Eu 3+ can improve the red emission of Eu 3+ ions under VUV excitation but only a part of the excitation energy in the excited 6P J states within Gd 3+ ions can be transferred to Eu 3+ ions for its red emission, and the nonradiative energy transfer efficiencies from the excited 6P J states within Gd 3+ to Eu 3+ were calculated. 相似文献
20.
3 H 4 and 3F 4 states of Tm in SrGdGa 3O 7 single crystal was evaluated. Tm-Tb energy transfer reduces effectively the lifetime of terminal level in a potential 3H 4- 3F 4 laser transition but gives rise to parasitic nonradiative relaxation of the initial 3H 4 level. SrGdGa 3O 7 crystal single doped with thulium possesses combination of properties advantageous for laser oscillations near 1.9 μm, namely
high rate of cross relaxation process leading to population buildup on the initial 3F 4 level and relatively high crystal field splitting of the ground 3H 6 level.
Received: 25 April 1996/Revised version: 10 October 1996 相似文献
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