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1.
The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride glass when excited by a 975 nm diode laser was studied in this paper. One typical ultraviolet upconversion luminescence lines positioned at 362.3 nm was found. It can be attributed to the five-photon upconversion luminescence transition of 1D2 → 3H6. Several visible upconversion luminescence lines at 451.1 nm, (477.9 nm, 462.5 nm), 648.7 nm, (680.5 nm, 699.5 nm) and (777.5 nm, 800.7 nm) were found also, which results from the fluorescence transitions of five-photon 1D2 → 3F4, three-photon 1G4 → 3H6, three-photon 1G4 → 3F4, two-photon 3F3 → 3H6 and two-photon 3H4 → 3H6 of Tm3+ ion, respectively. The theoretical analysis suggests that the upconversion mechanism of the 362.3 nm 1D2 → 3H6 upconversion luminescence is the cross energy transfer of {3H4(Tm3+) → 3F4(Tm3+), 1G4(Tm3+) → 1D2(Tm3+)} and {1G4(Tm3+) → 3F4(Tm3+), 3H4(Tm3+) → 1D2(Tm3+)} between Tm3+ ions. In addition, the upconversion luminescence of 1G4 and 3H4 state results from the sequential energy transfer {2F5/2(Yb3+) → 2F7/2(Yb3+), 3H4(Tm3+) → 1G4(Tm3+)} and {2F5/2(Yb3+) → 2F7/2(Yb3+), 3F4(Tm3+) → 3F2(Tm3+)} from Yb3+ ions to Tm3+ions, respectively.  相似文献   

2.
Upconversion emission and energy transfer processes in singly, doubly and triply doped tellurite glasses have been studied under 798 and 980 nm laser excitations. Emissions have been observed at 482, 544, 584, 655 nm and at 477, 655, 698, 800 nm corresponding to Tb3+: 5D4 → 7F6, 7F5, 7F4, 7FJ (J = 0, 1, 2, 3) and Tm3+: 1G4 → 3H6, 1G4 → 3F4, 3F3 → 3H6, 3H4 → 3H6 transitions, respectively. Among Tm3+, Yb3+and Tb3+ ions only Tm3+ has a ground state absorption at 798 nm excitation due to 3H4 ← 3H6 transition. For 980 nm excitation only Yb3+ can absorb the incident radiation. However, for both types of excitations, emission from all the three ions Tb, Yb and Tm has been observed. Possible mechanisms are proposed as follows: under 798 nm excitation Tm3+ ions are excited which excite Yb3+ ions through energy transfer. Finally “cooperative energy transfer” from a pair of Yb3+ ions to Tm3+ and Tb3+ ions takes place. Under 980 nm excitation Yb3+ ions absorb the incident energy and excite Tm3+ and Tb3+ ions via cooperative energy transfer. Variation of emission intensity with the ion concentrations of Yb3+, Tm3+ and Tb3+ has been studied. The lifetime of the 1G4 level has also been measured.  相似文献   

3.
In this paper, we present the spectral results of Dy3+ and Pr3+ (1.0 mol%) ions doped Bi2O3-ZnF2-B2O3-Li2O-Na2O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy3+:glass has shown two emission transitions 4F7/26H15/2 (482 nm) and 4F7/26H13/2 (576 nm) with an excitation at 390 nm wavelength and Pr3+:glass has shown a strong emission transition 1D23H4 (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy3+ and Pr3+ glasses have shown bright yellow and reddish colors, respectively, from their surfaces.  相似文献   

4.
Effect of composition on the structure, spontaneous and stimulated emission probabilities of various 1.0 mol% Tm2O3 doped (1−x)TeO2+(x)WO3 glasses were investigated using Raman spectroscopy, ultraviolet-visible-near-infrared (UV/VIS/NIR) absorption and luminescence measurements.Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f-4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the 1G4, 3F2, 3F3 and 3F4, 3H5 and 3H4 levels from the 3H6 ground level were observed. Integrated absorption cross-section of each band except that of 3H5 level was found to vary with the glass composition. Luminescence spectra of the samples were measured upon 457.9 nm excitation. Three emission bands centered at 476 nm (1G43H6 transition), 651 nm (1G43H4 transition) and 800 nm (1G43H5 transition) were observed. Spontaneous emission cross-sections together with the luminescence spectra measured upon 457.9 nm excitation were used to determine the stimulated emission cross-sections of these emissions.The effect of glass composition on the Judd-Ofelt parameters and therefore on the spontaneous and the stimulated emission cross-sections for the metastable levels of Tm3+ ions were discussed in detail. The effect of temperature on the stimulated emission cross-sections for the emissions observed upon 457.9 nm excitation was also discussed.  相似文献   

5.
In this paper, we present the photoluminescence properties of Pr3+-, Sm3+- and Dy3+-doped germanate glasses and glass ceramics. From the X-ray diffraction measurement, the host glass structure was determined. These glasses have shown strong absorption bands in the near-infrared (NIR) region. Compared to Pr3+-, Sm3+- and Dy3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the Ba2TiGe2O8 crystalline phase. For Pr3+-doped glass and glass ceramic, emission bands centered at 530 nm (3P03H5), 614 nm (3P03H6), 647 nm (3P03F2) and 686 nm (3P03F3) have been observed with 485 nm (3H43P0) excitation wavelength. Of them, 647 nm (3P03F2) has shown bright red emission. Emission bands of 4G5/26H5/2 (565 nm), 4G5/26H7/2 (602 nm) and 4G5/26H9/2 (648 nm) for the Sm3+:glass and glass ceramic, with excitation at 6H5/24F7/2 (405 nm) have been recorded. Of them, 4G5/26H7/2 (602 nm) has shown a bright orange emission. With regard to the Dy3+:glass and glass ceramic, a bright fluorescent yellow emission at 577 nm (4F9/26H13/2) has been observed, apart from 4F9/26H11/2 (667 nm) emission transition with an excitation at 454 nm (6H15/24I15/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr3+, Sm3+ and Dy3+:glasses and glass ceramics have been computed based on their measured full-width at half-maxima (FWHM, Δλ) and lifetimes (τm).  相似文献   

6.
Tm3+/Yb3+-codoped germanate-niobic (GN) and germanium-bismuth (GB) glasses have been synthesized by conventional melting and quenching method. Intense blue and weak red emissions centered at 477 and 650 nm, corresponding to the transitions 1G43H6 and 1G43H4, respectively, were observed at room temperature. The possible up-conversion mechanisms are discussed and estimated. GN glass showed a weaker up-conversion emission than GB glass, which is inconsistent with the prediction from the difference of maximum phonon energy between GN and GB glasses. In this paper, Raman spectroscopy was employed to investigate the origin of the difference in up-conversion luminescence in the two glasses. Compared with phonon side-band spectroscopy, Raman spectroscopy extracts more information including both phonon energy and phonon density. For the first time, our results reveal that, besides the maximum phonon energy, the phonon density of host glasses is also an important factor in determining the up-conversion efficiency.  相似文献   

7.
A series of Tm3+/Yb3+ co-doped lanthanum-zinc-lead-tellurite (TPZL) glasses pumped by a 980 nm laser diode (LD) were demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Effects of PbO content on the thermal stability, structure and upconversion properties of Tm3+/Yb3+ co-doped TPZL glasses had been investigated. The efficient visible upconversion fluorescences corresponding to the 1G43H6, 1G43F4 and 3H43H6 transitions of Tm3+ were observed under 980 nm excitation. The upconversion intensities of blue, red and near infrared emissions in Tm3+/Yb3+ co-doped TPZL glasses were obviously enhanced with increasing PbO content. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms had been evaluated by a proper rate equation model. Population density in different levels and coefficients of the energy transfer rate CDi (i=2, 4, 6) between Tm3+ and Yb3+ were estimated by fitting the simulated curves to the measured ones. The obtained three energy transfer coefficients CD2, CD4, and CD6 were determined to be 5.7×10−17, 1.3×10−16 and 8.6×10−17 cm3/s, respectively.  相似文献   

8.
Er-Tm-codoped Al2O3 thin films with different Tm to Er concentration ratios were synthesized by cosputtering from separated Er, Tm, Si, and Al2O3 targets. The temperature dependence of photoluminescence (PL) spectra was studied. A flat and broad emission band was achieved in the 1.4-1.7 μm and the observed 1470, 1533 and 1800 nm emission bands were attributed to the transitions of Tm3+: 3H4 → 3F4, Er3+: 4I13/2 → 4I15/2 and Tm3+: 3F4 → 3H6, respectively. The temperature dependence is rather complicated. With increasing measuring temperature, the peak intensity related to Er3+ ions increases by a factor of five, while the Tm3+ PL intensity at 1800 nm decreases by one order of magnitude. This phenomenon is attributed to a complicated energy transfer (ET) processes involving both Er3+ and Tm3+ and increase of phonon-assisted ET rate with temperature as well. It should be helpful to fully understand ET processes between Er and Tm and achieve flat and broad emission band at different operating temperatures.  相似文献   

9.
We studied the spectroscopic characteristics of telluride glass with the host composition (0.85)TeO2-(0.15)WO3, containing 0.25 and 1.0 mol% thulium oxide (Tm2O3). By analyzing the absorption spectra with the Judd-Ofelt theory, the average radiative lifetimes of 305±7.5 μs and 1.95±0.02 ms were determined for the 3F4 and 3H4 levels, respectively. Measured fluorescence lifetime of the 3F4 level decreased from 218 to 51 μs for the 0.25 and 1.0 mol% Tm2O3 doped samples, respectively, indicating the effect of boosted non-radiative decay at higher doping concentrations. A similar trend was observed for the 3H4 level, where the fluorescence lifetime decreased from 1.86 ms to 350 μs at these concentrations. The quenching of the 1460 nm (3F43H4) emission in favor of the 1800 nm (3H43H6) emission due to cross relaxation was further evident in the fluorescence spectra of the samples. The calculated stimulated emission cross sections (3.73±0.1×10−21 cm2 at 1460 nm and 6.57±0.07×10−21 cm2 at 1808 nm) reveal the potential importance of the Tm3+:(0.85)TeO2-(0.15)WO3 glass for applications in fiber-optic amplifiers and fiber lasers.  相似文献   

10.
Effect of Yb2O3 content on upconversion luminescence and mechanisms in Yb3+-sensitized Tm3+-doped oxyhalide tellurite glasses were investigated under 980 nm excitation. Intense blue and relatively weak red upconversion emission centered at 476 and 649 nm corresponding to the transitions 1G43H6 and 1G43H4 of Tm3+, respectively, are simultaneously observed at room temperature. The results show that upconversion blue and red emission intensities of Tm3+ first increase, reach its maximum at Yb2O3%=3 mol%, and then decrease with increasing Yb2O3 content. The effect of Yb2O3 content on upconversion intensity is discussed, and possible effect mechanisms are evaluated. The investigated results were conducing to increase upconversion luminescence efficiency of Tm3+.  相似文献   

11.
In this study, the principal role of Al2O3 on the features of the photoluminescence spectra of Tm3+ ion and upconversion phenomenon in Tm3+ and Er3+ codoped CaF2−Al2O3−P2O5−SiO2 glass system has been investigated. The concentration of Al2O3 is varied from 2 to 10 mol% while that of Er3+ and Tm3+ is fixed. IR and Raman spectral studies have indicated that there is a gradual increase in the degree of disorder in the glass network with increase in the concentration of Al2O3 up to 6.0 mol%. This is attributed to the presence of Al3+ ions in octahedral positions in larger proportions. When the glasses are doped with Tm3+ ions, the blue and red emissions were observed, whereas in Er3+ doped glasses blue, green and red emissions were observed. When the glasses are codoped with Tm3+ and Er3+ ions and excited at 790 nm, all the three emission lines were observed to be reinforced, especially in the glasses mixed with 6.0 mol% of Al2O3. The IR emission band detected at about 1.8 μm due to 3F43H6 transition of Tm3+ ions is also observed to be strengthened due to codoping. The reasons for enhancement in the intensity of various emission bands due to codoping have been identified and discussed with the help of rate equations for various emission transitions.  相似文献   

12.
Er3+-doped oxychloride germanate glasses have been synthesized by conventional melting and quenching method. Structural and thermal stability properties were obtained based on the Raman spectra and differential thermal analysis, indicating that PbCl2 plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/24I15/2, 4S3/24I15/2, and 4F9/24I15/2, respectively, were observed at room temperature. With increasing PbCl2 content, the intensity of green (525 and 546 nm) emissions increases significantly, while the red (657 nm) emission increases slowly. The results indicate that PbCl2 has more influence on the green emissions than the red emission in oxychloride germanate glasses. The possible upconversion luminescence mechanisms has also been estimated and discussed.  相似文献   

13.
Infrared to visible upconversion fluorescence in Yb,Tm:YAG single crystal   总被引:1,自引:0,他引:1  
Absorption spectrum from 400 to 2000 nm and upconversion fluorescence spectra under 940 nm pumping of YAG single crystal codoped with 5 at.% Yb3+ and 4 at.% Tm3+ were studied at room temperature. The blue upconversion emission centered at 483 nm corresponds to the transition 1G4 → 3H6, the emission band around 646 nm corresponds to the transition 1G4 → 3F4 of Tm3+. Energy transfer from Yb3+ to Tm3+ is mainly nonradiative and the transfer efficiency was experimentally assessed. The line strengths, transition probabilities and radiative lifetimes of 1G4 level were calculated by using Judd-Ofelt theory. Gain coefficient calculated from spectra shows that the upconversion corresponding with transitions 1G4 → 3H6 in YAG doped with Yb3+ and Tm3+ is potentially useful for blue light output.  相似文献   

14.
A luminescent material β-Na(Y1.5Na0.5)F6 doped with Tm3+ was synthesized by a solid-state reaction method for a steady phosphor of blue upconversion. Under the 671 nm laser excitation, the green emission band of 511 nm due to the 1D23H5 transition is obtained for the first time, while the ultraviolet emission band is also observed at 368 nm, associated with the 1D23H6 transition. Especially, a wide band of blue emissions is obtained at the wavelength region of 440-490 nm, originated mainly from the 1D23F4 (450 nm) and 1G43H6 (471-487 nm) transitions, which have potential application in tunable solid-state blue laser of Tm3+. The upconversion mechanism is explored in terms of the energy-level structures of Tm3+ ion and the power dependence of upconverted emission intensity, which is believed to be performed by excited-state absorption.  相似文献   

15.
The mechanism involved in the Tm3+(3F4)→Tb3+(7F0,1,2) 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.  相似文献   

16.
This paper reports on the absorption, visible and near-infrared luminescence properties of Nd3+, Er3+, Er3+/2Yb3+, and Tm3+ doped oxyfluoride aluminosilicate glasses. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. Decay lifetime curves were measured for the visible emissions of Er3+ (558 nm, green), and Tm3+ (650 and 795 nm), respectively. The near infrared emission spectrum of Nd3+ doped glass has shown full width at half maximum (FWHM) around 45 nm (for the 4F3/24I9/2 transition), 45 nm (for the 4F3/24I11/2 transition), and 60 nm (for the 4F3/24I13/2 transition), respectively, with 800 nm laser diode (LD) excitation. For Er3+, and Er3+/2Yb3+ co-doped glasses, the characteristic near infrared emission bands were spectrally centered at 1532 and 1544 nm, respectively, with 980 nm laser diode excitation, exhibiting full width at half maximum around 50 and 90 nm for the erbium 4I13/24I15/2 transition. The measured maximum decay times of 4I13/24I15/2 transition (at wavelength 1532 and 1544 nm) are about 5.280 and 5.719 ms for 1Er3+ and 1Er3+/2Yb3+ (mol%) co-doped glasses, respectively. The maximum stimulated emission cross sections for 4I13/24I15/2 transition of Er3+ and Er3+/Yb3+ are 10.81×10−21 and 5.723×10-21 cm2. These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification at low-loss telecommunication windows.  相似文献   

17.
Infrared-to-visible upconversion fluorescence property of Er3+/Yb3+-codoped novel bismuth-germanium glass under 975 nm LD excitation has been studied. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H11/24I15/2, 4S3/24I15/2, and 4F9/24I15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. The structure of the bismuth-germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel bismuth-germanium glass with low maximum phonon energy (∼750 cm−1) can be used as potential host material for upconversion lasers.  相似文献   

18.
Structural and infrared-to-visible upconversion fluorescence properties of Er3+/Yb3+-codoped oxychloride lead-germanium-bismuth glass have been studied. The Raman spectrum investigation indicates that PbCl2 plays an important role in the formation of glass network, and has an important influence on the upconversion luminescence owing to lower phonon energy. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/24I15/2, 4S3/24I15/2, and 4F9/24I15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation.  相似文献   

19.
Intense 1.8 μm and efficient 1.48 μm infrared emissions have been recorded in Tm3+-doped alkali-barium-bismuth-gallate (LKBBG) glasses with low phonon energies under the excitation of 792 nm diode laser. The maximum emission cross-sections for 1.8 and 1.48 μm emission bands are derived to be 6.26×10−21 and 3.34×10−21 cm2, respectively, and the peak values are much higher than those in Tm3+-doped ZBLAN glass. In low-concentration doping, the full-widths at half-maximum (FWHMs) of the two emission bands are 223 and 122 nm, and the quantum efficiencies of the 3F4 and 3H4 levels are proved to be ∼100% and 86%, respectively. When the doping concentration increases to 1 wt%, the quantum efficiency of the 3H4 level is reduced to 60% due to the cross-relaxation processes in high-concentration doping. Efficient 1.8 μm infrared emission in Er3+/Tm3+-codoped LKBBG glass has also been achieved under the excitation of 970 nm diode laser, and the probability and the efficiency of non-radiative energy transfer from Er3+ to Tm3+ are as high as 354 s−1 and 58.4%, respectively. Efficient and broad 1.8 and 1.48 μm infrared emission bands indicate that Tm3+-doped LKBBG glasses are suitable materials in developing S- and U-band amplifiers and 1.8 μm infrared laser.  相似文献   

20.
Phosphate (P2O5+K2O+BaO+Al2O3+Eu2O3) and fluorophosphate (P2O5+K2O+BaO+BaF2+Al2O3+Eu2O3) glasses with different Eu3+ ion concentrations have been prepared and characterized through optical absorption, photoluminescence and decay times. An intense red luminescence is observed from the 5D0 emitting level of Eu3+ ions in these glasses. The relative luminescence intensity ratio of 5D07F25D07F1 transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. The emission spectra of these glasses show a complete removal of degeneracy for the 5D07F1 and 5D07F2 transitions. Second and fourth rank crystal-field (CF) parameters have been calculated together with the CF strength parameter by assuming the C2v symmetry for the Eu3+ ions in both the phosphate and fluorophosphate glasses. Judd-Ofelt parameters have been evaluated from the luminescence intensity ratios of 5D07FJ (J=2, 4 and 6) to 5D07F1 transitions. These parameters have been used to derive radiative properties such as transition probabilities, branching ratios, radiative lifetimes and peak stimulated emission cross-sections for the 5D07FJ transitions. Decay curves of the 5D0 level of Eu3+ ions in these two Eu3+:glass systems have been measured by monitoring the 5D07F2 transition (611 nm) at room temperature. The experimental lifetime of the 5D0 level in the title glasses is found to be higher than Eu3+-doped niobium phosphate glasses. The analysis indicates that the lifetime of the 5D0 level is found to be less sensitive to the Eu3+ ion concentration and addition of BaF2 has no significant effect on the optical properties of Eu3+-doped phosphate glasses.  相似文献   

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