OSA's Digital Library

Journal of the Optical Society of America B

Journal of the Optical Society of America B

| OPTICAL PHYSICS

  • Editor: Henry Van Driel
  • Vol. 26, Iss. 10 — Oct. 1, 2009
  • pp: 1930–1938
« Show journal navigation

Strong 1.53 μ m to NIR–VIS–UV upconversion in Er-doped fluoride glass for high-efficiency solar cells

Svetlana Ivanova and Fabienne Pellé  »View Author Affiliations


JOSA B, Vol. 26, Issue 10, pp. 1930-1938 (2009)
http://dx.doi.org/10.1364/JOSAB.26.001930


View Full Text Article

Acrobat PDF (498 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Optical spectra of Er-doped modified ZBLAN glasses are studied at room temperature. Radiative quantum yields of the I 11 2 4 and I 13 2 4 levels are estimated from the experimentally measured lifetimes and from the spontaneous emission probabilities calculated from the Judd–Ofelt theory. The spectra of upconversion (UC) luminescence excited with 1.53 μ m cw Er fiber laser are investigated in a wide spectral domain [from the near-infrared (NIR) to UV]. Absolute UC efficiency (i.e., the ratio of UC luminescence power to the absorbed pump power) is experimentally measured; efficiency of up to 12.7% is obtained. A conclusion is made about perspectives of use of the studied glasses as upconverter material for solar cells of enhanced efficiency.

© 2009 Optical Society of America

1. INTRODUCTION

Two important issues govern the choice of the host to obtain a material with high UC efficiency. A host with a narrow phonon spectrum permits to prevent multiphonon relaxation from the excited Er levels. Multiphonon relaxation from the I1124 level, emitting at 1μm, dominates in most of the oxide hosts with phonon spectrum cut-off frequency about 1000cm1, and is partly suppressed in fluoride, chloride, chalcogenide, and bromide hosts with maximal phonon energy less than 600cm1. Another important issue is clustering of Er ions within the host. Nonradiative energy transfers with, in particular, cross-relaxations between Er ions are favored in materials containing groups of closely spaced Er ions or Er clusters. In the case of Er ions, due to the specific energy-levels diagram, energy transfer processes leading both to self-quenching of the luminescence and to UC are possible, whether being beneficial or detrimental for the whole UC efficiency. Finally, glassy or disordered hosts are preferred for the specific application as active layers for highly efficient solar cells: inhomogeneous broadening in absorption spectra of RE ions due to disorder of the host allows absorbing a larger part of the solar spectrum.

In this paper, we report on the results of a study of 1.5μm to NIR UC and absolute UC efficiency measurements in Er-doped fluorozirconate glasses. The goal of this study is to quantitatively evaluate the potential of the Er-doped modified ZBLAN glasses for use as an upconverter material in crystalline-silicon–based solar cells. Fluoro-zirconate glass was chosen as a host due to its low maximal phonon energy, broad bands in RE ions spectra doped in the glass, relatively easy synthesis and high chemical stability compared to chlorides or bromides, which demonstrate lower maximal phonon energy but usually are highly hygroscopic. We have studied glasses prepared following two distinct synthesis procedures affecting the dopant local environment and favoring or suppressing formation of groups of closely spaced Er ions or clusters. Although Er3+ spectroscopic properties in ZBLAN-type glasses have been extensively investigated, we have studied absorption spectra and calculated the intensity parameters, radiative transition probabilities, and branching ratios for the reason of probable change in spectroscopic parameters due to the modified Er3+ local environment. The intensity parameters of Er3+-doped ZBLAN-type glasses were obtained in [12

12. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Spectroscopic properties of Er3+ in fluorozirconate, germanate, tellurite and phosphate glasses,” Phys. Chem. Glass 37, 73–75 (1996).

, 13

13. F. Pellé, N. Gardant, and F. Auzel, “Effect of excited-state population density on nonradiative multiphonon relaxation rates of rare-earth ions,” J. Opt. Soc. Am. A 15, 667–679 (1998). [CrossRef]

, 14

14. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Judd–Ofelt parameters of rare earth ions in ZBLALi, ZBLAN and ZBLAK fluoride glasses,” Phys. Chem. Glass 35, 258–259 (1994).

, 15

15. M. D. Shinn, W. A. Sibley, M. G. Drexhage, and R. N. Brown, “Optical transitions of Er3+ ions in fluorozirconate glass,” Phys. Rev. B 27, 6635–6648 (1983). [CrossRef]

], radiative transition probabilities were calculated in [16

16. S. R. Bullock, B. R. Reddy, P. Venkateswarlu, S. K. Nash-Stevenson, and J. C. Fajardo, “Energy upconversion and spectroscopic studies of ZBLAN:Er3+,” Opt. Quantum Electron. 29, 83–92 (1997). [CrossRef]

]. The UC luminescence spectra of Er3+-doped ZBLAN-type glass under IR excitation at 1520nm are reported in [17

17. Ch. Xiaobo, “Study of up-conversion luminescence of Er:ZBLAN excited by 1520nm laser,” Opt. Commun. 242, 565–573 (2004). [CrossRef]

] along with the discussion of mechanisms leading to the population of the Er3+ radiative levels. In the present study we have measured the absolute efficiency of UC of radiation at 1.53μm to the NIR, visible (VIS), and UV spectral ranges in the Er-doped modified ZBLAN glasses. The results of the tests of photocurrent generation in a crystalline-silicon–based solar cell with the studied Er-doped ZBLAN glasses used as an upconverter at an illumination at 1.53μm will be published in a forthcoming paper.

The UC processes are intensively studied since the 1960s, when Bloembergen’s idea of the IR quantum counter was proposed [18

18. N. Bloembergen, “Solid state infrared quantum counters,” Phys. Rev. Lett. 2, 84–85 (1959). [CrossRef]

], and demonstrations of anti-Stokes emission in RE-doped solid-state inorganic materials were independently interpreted by F. Auzel [19

19. F. Auzel, C. R. Acad. Sci. (Paris) 262, 1016 (1966);

19. F. Auzel, C. R. Acad. Sci. (Paris) 263, 819–821 (1966).

, ] and by Ovsyankin and Feofilov [20

20. V. V. Ovsyankin and P. P. Feofilov, “Cooperative sensitization of luminescence in crystals activated with rare earth ions,” Sov. Phys. JETP Lett. 4, 471–474 (1966). [Zh. Eksp. & Teor. Fiz. Pis'ma 4, 471–474 (1966)].

]. However, only a few publications reporting on absolute UC efficiency measurements have appeared up to date [21

21. R. H. Page, K. I. Schaffers, P. A. Waide, J. B. Tassano, S. A. Payne, W. F. Krupke, and W. K. Bischel, “Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium,” J. Opt. Soc. Am. B 15, 996–1008 (1998). [CrossRef]

, 22

22. F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104, 139–174 (2004), and references therein. [CrossRef] [PubMed]

, 23

23. D. Chen, Y. Wang, Y. Yu, P. Huang, and F. Weng, “Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission,” J. Solid State Chem. 181, 2763–2767 (2008). [CrossRef]

, 24

24. Zh. Jin, Q. Nie, T. Xu, Sh. Dai, X. Shen, and X. Zhang, “Optical transitions and upconversion luminescence of Er3+Yb3+, codoped lead-zinc-tellurite oxide glass,” Mater. Chem. Phys. 104, 62–67 (2007). [CrossRef]

, 25

25. V. K. Rai, K. Kumar, and S. B. Rai, “Upconversion in Pr3+ doped tellurite glass,” Opt. Mater. 29, 873–878 (2007). [CrossRef]

, 26

26. Q. Nie, L. Lu, T. Xu, Sh. Dai, X. Shen, X. Liang, X. Zhang, and X. Zhang, “Upconversion luminescence of Er3+Yb3+-codoped natrium-germanium-bismuth glasses,” J. Phys. Chem. Solids 67, 2345–2350 (2006). [CrossRef]

]. These data are of extreme importance for estimation of real feasibility of approaches suggested for applications. To the best of our knowledge, this is the first report on the measurements of absolute efficiency of 1.5μm to NIR UC.

2. EXPERIMENTAL DETAILS

2A. Synthesis

In order to obtain glasses with different distribution of impurity ions, fluorozirconate glasses of two different types of composition were prepared: (i) diluted Er-doped glass Z17Er2% with composition 55.6% ZrF4,27.3% BaF2,2.9% LaF3,4.9% AlF3,6.8% NaF, 0.5%InF3 (Er concentration 3.151020cm3); and (ii) concentrated Er-doped glass Z18Er5% with composition 54.0% ZrF4,26.6% BaF2,2.8% LaF3,4.8% AlF3,6.6% NaF, 0.5%InF3 (Er concentration 8.071020cm3); according to the procedure proposed by F. Auzel [27

27. F. Auzel and D. Morin, French Patent B. F. N 96 13327, Procédé de fabrication de matériaux vitreux dopés et destinés à l'amplification optique ou laser, October 31, 1996.

]. Applying this procedure, different precursors were used for introducing the dopant ion into the host, which affected the spatial distribution of the impurity ions in the resulting glass and led to rather uniform distribution for the Z17Er2% sample and formation of groups of closely spaced Er ions or Er clusters for the Z18Er5% sample.

The constituent chemicals of 4N purity were melted in a Pt crucible at 850°C in inert argon atmosphere then poured into a copper plate preheated at 260°C and left for slow cooling inside the furnace. As a result, transparent glasses of light rose color were obtained.

For spectroscopic measurements, the samples were cut and polished in order to obtain thin plates with parallel faces. Concentration of Er ions per cubic centimeter in the obtained glasses was calculated on the basis of the results of the density measurements.

2B. Spectroscopic and Absolute Upconversion Efficiency Measurements

Absorption spectra were measured using the Varian CARY-5 spectrometer. Kinetics of luminescence from the I1324 and I1124 Er levels was measured at selective pulsed laser excitation (λexc=980 and 1530nm, respectively; emission of an optical parametric oscillator pumped by the 3rd harmonics of Thales Q-switched Nd:YAG laser; pulse duration 10ns, energy 3mJ per pulse). Luminescence in the IR was analyzed with a HR 250 Jobin–Yvon monochromator and detected with a PbS (at 2.7μm) or InGaAs (at 1.55μm) detector. Luminescence decays were recorded with a Tektronix TDS 350 oscilloscope.

Refractive index was measured with Abbe refractometer at 589.3nm.

Upconversion luminescence was excited with a cw pig-tailed Er fiber laser (ELT-100 IRE Polus Group) delivering power up to 100mW via a single-mode fiber with 8μm core diameter. A splitter and a photodiode integrated into the device permitted to control the excitation power. The IR luminescence in the range of 9001700nm was analyzed by a monochromator (SpectraPro 750, dispersion 1.2mmnm), detected by a liquid nitrogen cooled PbS detector, and corrected for spectral response of the system. Glass plates under study were brought as close as possible to the pumping laser fiber termination [Fig. 1a ], and the ensemble was introduced inside an integrating sphere covered with Spectralon™. An UC luminescence signal was delivered to a spectrometer (AVASpec-1024TEC) by an optical fiber. The whole setup (integrating sphere+spectrometer) is calibrated with the use of a halogen tungsten lamp (10W tungsten halogen fan-cooled Avalight-HAL). The scheme of setup for absolute UC efficiency measurements is shown in Fig. 1b. For both setups (with a monochromator and with an integrating sphere), the same sample holder [Fig. 1a] was used.

The Spectralon™ reflectance is still high (98%) at the pump wavelength; however, the pump radiation transmitted through the sample and reflected from the sphere inner surface does not constitute an additional source of excitation. When illuminating the sample with the pump beam diffused from the sphere surface, no UC signal was detected due to low pump-power density. This permits us to take into account only a single pass of the pump radiation through the sample. Furthermore, since the detection system does not respond at wavelengths longer than 1.1μm, the pump radiation arriving occasionally into the detection system does not introduce parasitic signals.

3. RESULTS AND DISCUSSION

3A. Absorption Spectra and Judd–Ofelt Calculations

Room temperature absorption cross-section spectra of Er:ZBLAN glasses recorded in the IR-VIS-UV are shown in Fig. 2 . At room temperature, the line shapes in the absorption cross-section spectra of both concentrated and diluted glass are very similar. The absorption cross-section at pump wavelength for the Z17Er2% and the Z18Er5% samples were σabs(1532nm)=0.42×1020cm2 and σabs(1532nm)=0.49×1020cm2, respectively. Weak absorption band around 820nm corresponding to the I1524I924 transition is not shown in Fig. 2 due to poor signal-to-noise ratio. The broad absorption band near 1.5μm, corresponding to the I1524I1324 transition, is located below the absorption edge of crystalline silicon (1.1μm). The large FWHM (70nm) of this band and the high integrated absorption cross-section σabs(ν)dν (1.29×1018cm for the Z17Er 2% sample and 1.41×1018cm for the Z18Er 5% sample) are convenient for pumping with a source characterized by a broadband spectrum such as the AM1.5 solar radiation spectrum.

From the absorption spectra, the Judd–Ofelt intensity parameters [28

28. B. R. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750–761 (1962). [CrossRef]

, 29

29. G. S. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511–520 (1962). [CrossRef]

], spontaneous radiative transition probabilities, and branching ratios for Er in the glasses under study were calculated following common procedure described, for instance, by A. Kermaoui and F. Pellé [30

30. A. Kermaoui and F. Pellé, “Synthesis and infrared spectroscopic properties of Tm3+-doped phosphate glasses,” J. Alloys Compd. 469, 601–608 (2009). [CrossRef]

]. The details will be published in a forthcoming paper. Reasonable values of the intensity parameters were obtained for both samples, they are represented in the Table 1 . Slight deviations from the intensity parameters obtained in [12

12. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Spectroscopic properties of Er3+ in fluorozirconate, germanate, tellurite and phosphate glasses,” Phys. Chem. Glass 37, 73–75 (1996).

, 13

13. F. Pellé, N. Gardant, and F. Auzel, “Effect of excited-state population density on nonradiative multiphonon relaxation rates of rare-earth ions,” J. Opt. Soc. Am. A 15, 667–679 (1998). [CrossRef]

, 14

14. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Judd–Ofelt parameters of rare earth ions in ZBLALi, ZBLAN and ZBLAK fluoride glasses,” Phys. Chem. Glass 35, 258–259 (1994).

, 15

15. M. D. Shinn, W. A. Sibley, M. G. Drexhage, and R. N. Brown, “Optical transitions of Er3+ ions in fluorozirconate glass,” Phys. Rev. B 27, 6635–6648 (1983). [CrossRef]

] are explained by different composition of the glass host, and, particularly, by a slightly different Er3+ local environment due to the special doping procedure. Using the obtained intensity parameters (summarized in Table 1 together with corresponding root mean square errors on electric–dipole oscillator strengths), the radiative transition probabilities, branching ratios, and radiative lifetimes for nine excited Er levels were calculated similarly to how it was done in [30

30. A. Kermaoui and F. Pellé, “Synthesis and infrared spectroscopic properties of Tm3+-doped phosphate glasses,” J. Alloys Compd. 469, 601–608 (2009). [CrossRef]

]. The results obtained for the samples Z17Er2% and Z18Er5% are represented in Table 1, together with central wavelengths of radiative transitions and the energy gaps separating the excited Er levels in ZBLAN glasses determined by Y. D. Huang et al. [31

31. Y. D. Huang, M. Mortier, and F. Auzel, “Stark level analysis for Er3+ -doped ZBLAN glass,” Opt. Mater. 17, 501–511 (2001). [CrossRef]

].

The lifetimes of the I1324 and I1124 Er levels were measured experimentally using selective pulsed laser excitation; the obtained results are summarized in Table 1. The luminescence decays were purely exponential for both levels in both samples. For the I1324 level, the measured lifetimes are slightly longer than calculated. This may be attributed to the influence of reabsorption. The lumin escence from the I1124 level was detected at 2.7μm (the I1124I1324 transition) in order to avoid reabsorption.

3B. Luminescence Spectra

The luminescence spectra of Er-doped fluorozirconate glasses excited by a cw laser-diode (LD) pumped Er fiber laser (λ=1532nm), are shown in Fig. 3 . The spectra in the UV–VIS–NIR spectral domain (3801100nm) were recorded using the setup with an integrating sphere, which permits absolute measurements of the power of the luminescence emitted by the sample. The spectra in the IR spectral domain (9001700nm) were corrected for the spectral response of the registration system and scaled in order to obtain the same luminescence power of the band at 0.98μm as that in spectra recorded using the setup with the integrating sphere. Both setups allow one to record spectra in energy per wavelength units. The as-obtained luminescence power spectra of Er-doped ZBLAN samples are shown in Fig. 3 in energy per wavelength units [Figs. 3a, 3b] and in photon flux per constant energy interval units [Figs. 3c, 3d]. The obtained UC luminescence spectra are in qualitative agreement with the results reported in [17

17. Ch. Xiaobo, “Study of up-conversion luminescence of Er:ZBLAN excited by 1520nm laser,” Opt. Commun. 242, 565–573 (2004). [CrossRef]

].

For both samples, the most intensive emission bands are observed near 1.5μm (transition I1324I1524, resonant with excitation) and near 0.98μm (transition I1124I1524). Several weaker luminescence bands are observed in the NIR (overlapped bands at 820nm, transition I924I1524 and at 850nm, transition S324I1324), red (660nm, transition F924I1524), green (550nm, transition S324I1524), and blue-UV (410nm, transition G922I1524) spectral domains. Note that, for population of the initial levels of these transitions, absorption of at least two (I924 level), three (F924 and S324 levels), or four (G922 level) excitation photons are needed. The energy-levels scheme of Er permits various paths for population of these levels; the most probable processes are summarized in Fig. 4a .

A detailed study of energy transfer in fluorozirconate glasses is needed in order to identify the most efficient mechanisms of population of excited levels I1124, I924, F924, S324, and G922 upon excitation at λexc=1532nm; here we have only identified possible processes of population, relying on the consideration of the Er energy-levels scheme. Since in this paper we are especially interested in the absolute measurements of 1.5μm NIR and VIS conversion efficiency, the detailed study of energy transfer in fluorozirconate glasses will be published in a forthcoming paper.

3C. Upconversion Yield

In order to estimate the fraction of absorbed excitation photons that are subsequently reemitted in the anti-Stokes region, we have followed the procedure proposed by J. F. Suyver et al. [33

33. J. F. Suyver, J. Grimm, K. W. Krämer, and H. U. Güdel, “Highly-efficient near-infrared to visible upconversion process in NaYF4Er3+,Yb3+,” J. Lumin. 114, 53–59 (2005). [CrossRef]

].

The fraction of all photons emitted in the band i is calculated as
fi=ΦiintjΦjint,
(2)
where Φiint=ν0ν1Φi(ν)dν denotes the area under the emission band i in the luminescence spectrum observed in the frequency domain between ν0 and ν1, displayed as a photon flux per constant energy interval [see Figs. 3c, 3d], and summation is over all luminescence bands. Further, let pi denote the number of excitation photons required to induce the emission in the band i. Then the product piΦiint is the (minimum) number of excitation photons required to induce the emission in the band i.

Next, we make an important assumption that each absorbed photon contributes to the emission of a photon, i.e., the depopulation of all the radiative excited levels is only possible via radiative transition to the ground state or UC via excited-state absorption (ESA) or energy transfer upconversion (ETU). Relying on this assumption, the fraction Ri of absorbed excitation photons emitted in the band i can be calculated as follows:
Ri=piΦiintjpjΦjint.
(3)
The assumption made in Eq. (3) implies that, for each emitting level,
  1. radiative relaxation dominates multiphonon relaxation;
  2. branching ratios of the transitions terminating at the ground state are close to unity;
  3. radiative relaxation dominates cross-relaxation leading to selfquenching of luminescence or UC.
Before the discussion of the results of calculation of the fractions Ri using Eq. (3), we will discuss the criteria (i)–(iii), paying the most attention to the I1324 and I1124 excited levels, since the most intensive bands in the luminescence spectra (Fig. 3) arise from these levels.

(ii) The requirement on the branching ratios of radiative transitions is not fully satisfied for the I1124 and the S324 levels. However, the weak intensity of luminescence of the transitions originating from the S324 level with respect to that originating from the I1124 and I1324 levels permits us to assume that the large branching ratio β(S324I1324)0.28 (Table 1) will not introduce significant error. The relatively high branching ratio obtained for the I1124I1324 transition β(I1124I1324)=0.18 (Table 1) implies that 18% of radiative transitions originating from the I1124 level, populated essentially by UC via ETU or ESA at 1.53μm pumping, provoke luminescence in the Stokes region (2.7μm) and are not taken into account in the luminescence spectra presented in Fig. 3. Consequently, the total fraction of absorbed excitation photons used for UC luminescence calculated using the Eq. (3) may be slightly underestimated. For other excited levels the branching ratios for transitions terminating at excited levels do not exceed 5% (Table 1) and should not introduce any significant error.

(iii) The energy-levels scheme of Er does not offer any cross-relaxation scheme leading to self-quenching of luminescence for the I1124 and I1324 levels, and the requirement of domination of radiative relaxation over cross-relaxation leading to self-quenching is satisfied for both levels. This is also supported by the fact that the decays of luminescence from these levels are purely exponential. Concerning higher energy excited levels, concentration self-quenching is usually observed in fluoride hosts for the luminescence originating from the S324 and G922 levels for Er concentrations above 1%. Again, we suppose that weak luminescence from these levels compared to the luminescence from the I1324 and I1124 levels permits us to suggest that self-quenching of luminescence from the S324 and G922 levels does not introduce significant error. The role of energy transfer processes in 1.53μm to 0.98 and VIS upconversion will be discussed in a forthcoming paper.

The fractions Ri of absorbed excitation photons emitted in the band i, calculated using Eq. (3), are presented in the Tables 2, 3 . The large fraction of absorbed photons reemitted in the NIR and VIS with the Z18Er5% sample (44.5% on total, in the 1.10.38μm region) proves that this glass is very promising for use in the UC devices.

For real applications, the fraction of energy emitted in a specific spectral domain ηiexp seems to be a more convenient parameter to characterize an UC material:
ηiexp=λ0λ1PmeasUC(λ)dλPlumint.
(4)
Here, PmeasUC(λ) represents the UC luminescence power displayed in energy per nanometer units [see Fig. 3a, 3b], and Plumint=380nm1100nmPmeasUC(λ)dλ the total power emitted in the whole spectral range of emission. The calculated fractions ηiexp from the UC luminescence spectra are gathered in Tables 2, 3.

3D. Discussion

The relevant correction coefficients may be calculated as
Γi=ν0ν1Φi(ν)hνdνpihνpumpν0ν1Φi(ν)dν=ν0ν1Φi(ν)νdνpiνpumpν0ν1Φi(ν)dν,
(5)
where ν0ν1Φi(ν)hνdν represents the power emitted in the band i, and the product pihνpumpν0ν1Φi(ν)dν represents the (minimum) power required to induce this luminescence. The calculated correction coefficients Γi are listed in the Tables 2, 3.

Total luminescence energy yield can be calculated as the ratio of luminescence power emitted in the whole spectral range Plumint=380nm1100nmPmeasUC(λ)dλ to the absorbed pump power ηtotexp=PlumintPabspump. The total luminescence energy yields of 38% and 33% were obtained for the samples Z17Er2% and Z18Er5%, respectively. Then, the absolute energy yields of 1.5μm0.98μm UC can be obtained: η2expηtotexp=7.4% and η2expηtotexp=11.5% for the samples Z17Er2% and Z18Er5%, respectively. Similarly the absolute energy yields of 1.5μmNIR–VIS UC were obtained as i=26ηiexpηtotexp=8.1% and i=26ηiexpηtotexp=12.7% for the samples Z17Er2% and Z18Er5%, respectively.

The experimentally measured total luminescence yields ηtotexp are lower than 100% in both samples under study. This may be partly explained as being due to possible losses in UC signal measured with the help of the integrating sphere. These losses are due to the fact that the reflectance of the metallic sample holder is generally lower than that of Spectralon™. However, we do not believe that more than 50% of luminescence could be lost because of low sample holder reflectance. A similar experimental setup with the same integrating sphere and detection system was used for the measurements of absolute efficiency of UC of 0.98μm radiation to the VIS [34

34. S. E. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “New concept for efficient upconverter materials,” presented at the Journées Annuelles de la Société Française de Métallurgie et de Matériaux, Paris, France, 3–6 June 2008; Conference program, abstract I-3-27.

, 35

35. S. E. Ivanova, A. M. Tkachuk, F. Pellé, M.-F. Joubert, Y. Guyot, and V. P. Gapontzev, “Energy transfer in RE-doped double fluoride crystals for diode pumped upconversion lasers,” presented at the 13th International Conference on Laser Optics, St. Petersburg, Russia, 23–28 June 2008, Technical program, p. ThR1-p64.

, 36

36. F. Pellé, S. E. Ivanova, B. Viana, and A. M. Tkachuk, “Characterization of upconversion materials based on Er-Yb doped fluoride crystals,” presented at the 15th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter (ICL 2008), Lyon, France, 7–11 July 2008, Book of Abstracts, We-P-060, p. 494.

, 37

37. S. Ivanova, F. Pellé, B. Viana, and A. Tkachuk, “IR to VIS upconversion in Er and Yb doped low phonon energy crystals: spectroscopic study and absolute efficiency measurements,” presented at the 3rd EPS-QEOD EUROPHOTON Conference on Solid-State, Fiber and Waveguided Light Sources, Paris, France, 2–5 September 2008, Conference Digest, THp13, p.46, Technical Digest on CD-ROM.

, 38

38. S. I. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “Thin film concepts for photon addition materials,” presented at the 23rd European Photovoltaic Solar Energy Conference and Exhibition, Valence, Spain, 1–5 September 2008, Conference program, abstract 1DV.2.56.

]; no significant loss of luminescence signal was detected.

Probable channels of relaxation of the excitation energy absorbed by the samples except luminescence in the 1.70.38μm domain are considered below.

First, as was discussed above, the reduced quantum yield of luminescence from the I1124 level (η=66.5% and η=76% for the Z17Er2% and Z18Er5% samples, respectively) may be attributed to multiphonon relaxation or quenching on uncontrolled impurities. This can partly explain the reduction of the total luminescence yield.

Another source of losses may originate from efficient nonradiative relaxation of excitation energy due to thermalization of the emitting levels and MPNR between closely spaced levels [e.g., I924I1124, process MPNR1 in Fig. 4a, or F724H1122S324, process MPNR2 in Fig. 4a] in a case when radiative relaxation from Er excited levels is preceded by multiple energy transfers. This hypothesis needs further investigation on the basis of a study of energy transfer processes in the considered Er-doped glasses.

Finally, the quenching of luminescence due to energy migration to eventual traps via highly populated I1324 level characterized by milliseconds-range lifetime, quantum yields close to 100% and typically very high migration rate in fluoride hosts, cannot be completely excluded.

The obtained results provide some evidence that the reliability of the results of estimations of UC efficiencies based on the analysis of luminescence spectra is limited if absolute measurements of UC luminescence intensity have not been performed. In addition to the analysis of luminescence spectrum, the absolute measurements of UC efficiency as it has been described [39

39. Z. Pan, S. H. Morgan, K. Dyer, A. Ueda, and H. Liu, “Host-dependent optical transitions of Er3+ ions in lead-germanate and lead-tellurium-germanate glasses,” J. Appl. Phys. 79, 8906–8913 (1996). [CrossRef]

, 40

40. R. S. Quimby, M. G. Drexhage, and M. J. Suscavage, “Efficient frequency up-conversion via energy transfer in fluoride glasses,” Electron. Lett. 23, 32–34 (1987). [CrossRef]

, 41

41. F. Vetrone, J.-C. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “980nm excited upconversion in an Er-doped ZnOTeO2 glass,” Appl. Phys. Lett. 80, 1752–1754 (2002). [CrossRef]

] or using a setup with integrating sphere can be proposed as a mean to accomplish the characterization of UC material.

4. CONCLUSIONS

In this paper we report on the results of absolute upconversion (UC) efficiency (i.e., the ratio of UC luminescence power to the absorbed pump power) measurements in Er-doped fluorozirconate glasses in the limiting case of high-excitation pump power.

Absolute UC efficiency of 1.532μm to NIR and VIS of 8.1% and 12.7% was obtained in Er-doped ZBLAN glasses Z17Er2% and Z18Er5%, respectively, under excitation with 75mW cw pig-tailed Er fiber laser. The most part of UC emission energy is contained in the NIR part of the spectrum (at 1μm), absolute 1.5μmto0.98μm UC efficiency is 7.4% (Z17Er2%) and 11.5% (Z18Er5%). The studied glasses are promising for application as an active layer of UC solar cells with enhanced efficiency, since the 0.98μm light has an absorption depth of only 100μm and is thus strongly absorbed in a wafer-based silicon solar cell. For crystalline-silicon–based solar cells, approximately a half of the energy contained in the VIS part of the UC spectrum will be released as heat during thermalization of hot carriers created after absorption of VIS photons. To the best of our knowledge, this is the first report on the measurements of absolute efficiency of 1.5μm to NIR UC.

The results of this study also reveal the problem of dual effect of energy transfer processes on efficiency of UC. The energy transfer processes represent, at the same time, efficient channels of high-excited-levels population via ETU and sources of losses via luminescence self-quenching accompanied by dissipation of energy due to phonon-assisted nonradiative relaxation. Choosing the correct dopant concentration, which governs the efficiency of energy transfer, is of great importance especially in cases when ESA is slightly off-resonant and, consequently, has poor efficiency. In the studied Er-doped ZBLAN glasses the higher absolute UC efficiency was demonstrated with the Z18Er5 sample, where dopant concentration is higher, and the synthesis favors formation of Er clusters or groups of closely spaced dopant ions. The obtained absolute UC efficiency is among the highest values published for 0.98μm to VIS upconversion. This permits us to make a conclusion about the positive role of energy transfer in the hosts under study, in spite of relatively low overall luminescence yield achieved, which is attributed mostly to the dissipation of excitation energy via phonon-assisted nonradiative relaxation accompanying multiple energy transfers.

ACKNOWLEDGMENTS

This work is supported by the French National Agency for Research (ANR), program “Solar Photovoltaics,” project “Very high efficiency and photovoltaic innovation” (THRI-PV). The authors acknowledge partial support from the Russian Foundation for Basic Research (RFBR), grant 07-02-01063.

Table 1. Calculated Spectroscopic Parameters of Radiative Transitions and Judd–Ofelt Intensity Parameters (Ωn) of the Er3+ Ion in the Z17Er2% and Z18Er5% Glassesa

table-icon
View This Table
| View All Tables

Table 2. Details for Emission Bands “i(i=15) Resulting from the Z17Er2% Samplea

table-icon
View This Table
| View All Tables

Table 3. Details For Emission Bands “i(i=15) Resulting from the Z18Er5% Samplea

table-icon
View This Table
| View All Tables
Fig. 1 Experimental setup for absolute UC efficiency measurements. (a) Sample is brought as close as possible to the fiber termination and attached to a metallic sample holder. (b) Schematic of experimental setup. Luminescence excitation source: cw pig-tailed Er fiber laser, λexc=1.532μm, pump power=75mW (stabilized, real-time control provided by integrated splitter and photodiode); a single-mode fiber with a core diameter 8μm. Integrating sphere: Avasphere; sphere diameter 5cm, sample port diameter 1cm, knife-edge sphere covered with Spectralon™. IR-UV-VIS spectrometer: AVASpec-1024TEC thermo-electric-cooled CCD fiber-optic spectrometer (75mm focal length). UC luminescence signal arrives on the end-face of an optical fiber in such a way that only diffused reflected luminescence is collected.
Fig. 2 Room-temperature absorption spectra of Er-doped ZBLAN glass (sample Z18Er5%) in the (a) IR and (b) UV-VIS spectral domains. Absorption bands correspond to transition from the ground state I1524 to the excited states listed in the figures.
Fig. 3 Luminescence spectra of Er-doped ZBLAN glasses, (a, c) sample Z17Er2% and (b, d) sample Z18Er5%. Note that in (c, d) the photon flux of the UC luminescence bands in the interval of 1100027000cm1 (3- and 4-photon processes) is multiplied by a factor of 20, and the photon flux of the luminescence band at 6500cm1 (1 photon process) is multiplied by (c) a factor of 0.2 and (d) 0.5. Excitation: wavelength is shown by an arrow. Excitation power is 75mW. Identification of transitions corresponding to the luminescence bands is shown in the figures.
Fig. 4 Energy-levels scheme of Er3+ ion. (a) Mechanisms of population of excited Er levels. Absorption of pump radiation (λexc=1532nm): ground-state absorption (GSA) and excited-state absorptions (ESA1–ESA3) indicated by upward arrows; multiphonon nonradiative relaxations (MPNR1 and MPNR2) indicated by waved arrows; energy transfers (UC1UC4); and radiative transitions indicated by downward arrows. Numbers near arrows denoting radiative transitions are wavelengths of luminescence in nanometers. (b) Losses of absorbed pump energy. Upward arrows, GSA and ESA; waved arrows, nonradiative relaxation providing thermalization of Stark sublevels of each multiplet and introducing losses; downward arrow, luminescence (LUM).
1.

Sh. F. Lim, R. Riehn, W. S. Ryu, N. Khanarian, Ch. Tung, D. Tank, and R. H. Austin, “In vivo and scanning electron microscopy imaging of upconverting nanophosphors in caenorhabditis elegans,” Nano Lett. 6, 169–174 (2006). [CrossRef] [PubMed]

2.

A. Brenier, “Upconversion lasers,” Encyclopedia of Modern Optics, 508–519 (2005).

3.

J. F. Massicott, M. C. Brierley, R. Wyatt, S. T. Davey, and D. Szebesta, “Low threshold, diode pumped operation of a green, Er3+ doped fluoride fibre laser,” Electron. Lett. 29, 2119–2120 (1993). [CrossRef]

4.

J. Y. Allain, M. Monerie, and H. Poignant, “Tunable green upconversion erbium fibre laser,” Electron. Lett. 28, 111–113 (1992). [CrossRef]

5.

H. Tobben, “Room temperature CW fibre laser at 3.5μm in Er3+ doped ZBLAN glass,” Electron. Lett. 28, 1361–1362 (1992). [CrossRef]

6.

L. Aigouy, G. Tessier, M. Mortier, and B. Charlot, “Scanning thermal imaging of microelectronic circuits with a fluorescent nanoprobe,” Appl. Phys. Lett. 87, 184105 (2005). [CrossRef]

7.

T. Trupke, M. A. Green, and P. Würfel, “Improving solar cell efficiencies by up-conversion of sub-band-gap light,” J. Appl. Phys. 92, 4117–4122 (2002). [CrossRef]

8.

A. Shalav, B. S. Richards, and M. A. Green, “Luminescent layers for enhanced silicon solar cell performance: Up-conversion,” Sol. Energy Mater. Sol. Cells 91, 829–842 (2007). [CrossRef]

9.

T. Trupke, A. Shalav, B. S. Richards, P. Würfel, and M. A. Green, “Efficiency enhancement of solar cells by luminescent up-conversion of sunlight,” Sol. Energy Mater. Sol. Cells 90, 3327–3338 (2006). [CrossRef]

10.

S. Ivanova, F. Pellé, A. Tkachuk, M.-F. Joubert, Y. Guyot, and V. P. Gapontzev, “Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters,” J. Lumin. 128, 914–917 (2008). [CrossRef]

11.

W. Shockley and H. J. Queisser, “Detailed balance limit of efficiency of p-n junction solar cells,” J. Appl. Phys. 32, 510–519 (1961). [CrossRef]

12.

J. P. McDougall, D. B. Hollis, and J. P. Payne, “Spectroscopic properties of Er3+ in fluorozirconate, germanate, tellurite and phosphate glasses,” Phys. Chem. Glass 37, 73–75 (1996).

13.

F. Pellé, N. Gardant, and F. Auzel, “Effect of excited-state population density on nonradiative multiphonon relaxation rates of rare-earth ions,” J. Opt. Soc. Am. A 15, 667–679 (1998). [CrossRef]

14.

J. P. McDougall, D. B. Hollis, and J. P. Payne, “Judd–Ofelt parameters of rare earth ions in ZBLALi, ZBLAN and ZBLAK fluoride glasses,” Phys. Chem. Glass 35, 258–259 (1994).

15.

M. D. Shinn, W. A. Sibley, M. G. Drexhage, and R. N. Brown, “Optical transitions of Er3+ ions in fluorozirconate glass,” Phys. Rev. B 27, 6635–6648 (1983). [CrossRef]

16.

S. R. Bullock, B. R. Reddy, P. Venkateswarlu, S. K. Nash-Stevenson, and J. C. Fajardo, “Energy upconversion and spectroscopic studies of ZBLAN:Er3+,” Opt. Quantum Electron. 29, 83–92 (1997). [CrossRef]

17.

Ch. Xiaobo, “Study of up-conversion luminescence of Er:ZBLAN excited by 1520nm laser,” Opt. Commun. 242, 565–573 (2004). [CrossRef]

18.

N. Bloembergen, “Solid state infrared quantum counters,” Phys. Rev. Lett. 2, 84–85 (1959). [CrossRef]

19.

F. Auzel, C. R. Acad. Sci. (Paris) 262, 1016 (1966);

F. Auzel, C. R. Acad. Sci. (Paris) 263, 819–821 (1966).

20.

V. V. Ovsyankin and P. P. Feofilov, “Cooperative sensitization of luminescence in crystals activated with rare earth ions,” Sov. Phys. JETP Lett. 4, 471–474 (1966). [Zh. Eksp. & Teor. Fiz. Pis'ma 4, 471–474 (1966)].

21.

R. H. Page, K. I. Schaffers, P. A. Waide, J. B. Tassano, S. A. Payne, W. F. Krupke, and W. K. Bischel, “Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium,” J. Opt. Soc. Am. B 15, 996–1008 (1998). [CrossRef]

22.

F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104, 139–174 (2004), and references therein. [CrossRef] [PubMed]

23.

D. Chen, Y. Wang, Y. Yu, P. Huang, and F. Weng, “Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission,” J. Solid State Chem. 181, 2763–2767 (2008). [CrossRef]

24.

Zh. Jin, Q. Nie, T. Xu, Sh. Dai, X. Shen, and X. Zhang, “Optical transitions and upconversion luminescence of Er3+Yb3+, codoped lead-zinc-tellurite oxide glass,” Mater. Chem. Phys. 104, 62–67 (2007). [CrossRef]

25.

V. K. Rai, K. Kumar, and S. B. Rai, “Upconversion in Pr3+ doped tellurite glass,” Opt. Mater. 29, 873–878 (2007). [CrossRef]

26.

Q. Nie, L. Lu, T. Xu, Sh. Dai, X. Shen, X. Liang, X. Zhang, and X. Zhang, “Upconversion luminescence of Er3+Yb3+-codoped natrium-germanium-bismuth glasses,” J. Phys. Chem. Solids 67, 2345–2350 (2006). [CrossRef]

27.

F. Auzel and D. Morin, French Patent B. F. N 96 13327, Procédé de fabrication de matériaux vitreux dopés et destinés à l'amplification optique ou laser, October 31, 1996.

28.

B. R. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750–761 (1962). [CrossRef]

29.

G. S. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511–520 (1962). [CrossRef]

30.

A. Kermaoui and F. Pellé, “Synthesis and infrared spectroscopic properties of Tm3+-doped phosphate glasses,” J. Alloys Compd. 469, 601–608 (2009). [CrossRef]

31.

Y. D. Huang, M. Mortier, and F. Auzel, “Stark level analysis for Er3+ -doped ZBLAN glass,” Opt. Mater. 17, 501–511 (2001). [CrossRef]

32.

D. L. Dexter and J. H. Schulman, “Theory of concentration quenching in inorganic phosphors,” J. Chem. Phys. 22, 1063–1070 (1954). [CrossRef]

33.

J. F. Suyver, J. Grimm, K. W. Krämer, and H. U. Güdel, “Highly-efficient near-infrared to visible upconversion process in NaYF4Er3+,Yb3+,” J. Lumin. 114, 53–59 (2005). [CrossRef]

34.

S. E. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “New concept for efficient upconverter materials,” presented at the Journées Annuelles de la Société Française de Métallurgie et de Matériaux, Paris, France, 3–6 June 2008; Conference program, abstract I-3-27.

35.

S. E. Ivanova, A. M. Tkachuk, F. Pellé, M.-F. Joubert, Y. Guyot, and V. P. Gapontzev, “Energy transfer in RE-doped double fluoride crystals for diode pumped upconversion lasers,” presented at the 13th International Conference on Laser Optics, St. Petersburg, Russia, 23–28 June 2008, Technical program, p. ThR1-p64.

36.

F. Pellé, S. E. Ivanova, B. Viana, and A. M. Tkachuk, “Characterization of upconversion materials based on Er-Yb doped fluoride crystals,” presented at the 15th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter (ICL 2008), Lyon, France, 7–11 July 2008, Book of Abstracts, We-P-060, p. 494.

37.

S. Ivanova, F. Pellé, B. Viana, and A. Tkachuk, “IR to VIS upconversion in Er and Yb doped low phonon energy crystals: spectroscopic study and absolute efficiency measurements,” presented at the 3rd EPS-QEOD EUROPHOTON Conference on Solid-State, Fiber and Waveguided Light Sources, Paris, France, 2–5 September 2008, Conference Digest, THp13, p.46, Technical Digest on CD-ROM.

38.

S. I. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “Thin film concepts for photon addition materials,” presented at the 23rd European Photovoltaic Solar Energy Conference and Exhibition, Valence, Spain, 1–5 September 2008, Conference program, abstract 1DV.2.56.

39.

Z. Pan, S. H. Morgan, K. Dyer, A. Ueda, and H. Liu, “Host-dependent optical transitions of Er3+ ions in lead-germanate and lead-tellurium-germanate glasses,” J. Appl. Phys. 79, 8906–8913 (1996). [CrossRef]

40.

R. S. Quimby, M. G. Drexhage, and M. J. Suscavage, “Efficient frequency up-conversion via energy transfer in fluoride glasses,” Electron. Lett. 23, 32–34 (1987). [CrossRef]

41.

F. Vetrone, J.-C. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “980nm excited upconversion in an Er-doped ZnOTeO2 glass,” Appl. Phys. Lett. 80, 1752–1754 (2002). [CrossRef]

OCIS Codes
(160.2750) Materials : Glass and other amorphous materials
(160.4330) Materials : Nonlinear optical materials
(160.4760) Materials : Optical properties
(160.5690) Materials : Rare-earth-doped materials
(300.6280) Spectroscopy : Spectroscopy, fluorescence and luminescence
(300.6410) Spectroscopy : Spectroscopy, multiphoton

ToC Category:
Materials

History
Original Manuscript: March 18, 2009
Revised Manuscript: June 26, 2009
Manuscript Accepted: June 29, 2009
Published: September 18, 2009

Virtual Issues
October 8, 2009 Spotlight on Optics

Citation
Svetlana Ivanova and Fabienne Pellé, "Strong 1.53 μm to NIR-VIS-UV upconversion in Er-doped fluoride glass for high-efficiency solar cells," J. Opt. Soc. Am. B 26, 1930-1938 (2009)
http://www.opticsinfobase.org/josab/abstract.cfm?URI=josab-26-10-1930


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. Sh. F. Lim, R. Riehn, W. S. Ryu, N. Khanarian, Ch. Tung, D. Tank, and R. H. Austin, “In vivo and scanning electron microscopy imaging of upconverting nanophosphors in caenorhabditis elegans,” Nano Lett. 6, 169-174 (2006). [CrossRef] [PubMed]
  2. A. Brenier, “Upconversion lasers,” Encyclopedia of Modern Optics, 508-519 (2005).
  3. J. F. Massicott, M. C. Brierley, R. Wyatt, S. T. Davey, and D. Szebesta, “Low threshold, diode pumped operation of a green, Er3+ doped fluoride fibre laser,” Electron. Lett. 29, 2119-2120 (1993). [CrossRef]
  4. J. Y. Allain, M. Monerie, and H. Poignant, “Tunable green upconversion erbium fibre laser,” Electron. Lett. 28, 111-113 (1992). [CrossRef]
  5. H. Tobben, “Room temperature CW fibre laser at 3.5 μm in Er3+ doped ZBLAN glass,” Electron. Lett. 28, 1361-1362 (1992). [CrossRef]
  6. L. Aigouy, G. Tessier, M. Mortier, and B. Charlot, “Scanning thermal imaging of microelectronic circuits with a fluorescent nanoprobe,” Appl. Phys. Lett. 87, 184105 (2005). [CrossRef]
  7. T. Trupke, M. A. Green, and P. Würfel, “Improving solar cell efficiencies by up-conversion of sub-band-gap light,” J. Appl. Phys. 92, 4117-4122 (2002). [CrossRef]
  8. A. Shalav, B. S. Richards, and M. A. Green, “Luminescent layers for enhanced silicon solar cell performance: Up-conversion,” Sol. Energy Mater. Sol. Cells 91, 829-842 (2007). [CrossRef]
  9. T. Trupke, A. Shalav, B. S. Richards, P. Würfel, and M. A. Green, “Efficiency enhancement of solar cells by luminescent up-conversion of sunlight,” Sol. Energy Mater. Sol. Cells 90, 3327-3338 (2006). [CrossRef]
  10. S. Ivanova, F. Pellé, A. Tkachuk, M.-F. Joubert, Y. Guyot, and V. P. Gapontzev, “Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters,” J. Lumin. 128, 914-917 (2008). [CrossRef]
  11. W. Shockley and H. J. Queisser, “Detailed balance limit of efficiency of p-n junction solar cells,” J. Appl. Phys. 32, 510-519 (1961). [CrossRef]
  12. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Spectroscopic properties of Er3+ in fluorozirconate, germanate, tellurite and phosphate glasses,” Phys. Chem. Glass 37, 73-75 (1996).
  13. F. Pellé, N. Gardant, and F. Auzel, “Effect of excited-state population density on nonradiative multiphonon relaxation rates of rare-earth ions,” J. Opt. Soc. Am. A 15, 667-679 (1998). [CrossRef]
  14. J. P. McDougall, D. B. Hollis, and J. P. Payne, “Judd-Ofelt parameters of rare earth ions in ZBLALi, ZBLAN and ZBLAK fluoride glasses,” Phys. Chem. Glass 35, 258-259 (1994).
  15. M. D. Shinn, W. A. Sibley, M. G. Drexhage, and R. N. Brown, “Optical transitions of Er3+ ions in fluorozirconate glass,” Phys. Rev. B 27, 6635-6648 (1983). [CrossRef]
  16. S. R. Bullock, B. R. Reddy, P. Venkateswarlu, and S. K. Nash-Stevenson, and J. C. Fajardo, “Energy upconversion and spectroscopic studies of ZBLAN:Er3+,” Opt. Quantum Electron. 29, 83-92 (1997). [CrossRef]
  17. Ch. Xiaobo, “Study of up-conversion luminescence of Er:ZBLAN excited by 1520 nm laser,” Opt. Commun. 242, 565-573 (2004). [CrossRef]
  18. N. Bloembergen, “Solid state infrared quantum counters,” Phys. Rev. Lett. 2, 84-85 (1959). [CrossRef]
  19. F. Auzel, C. R. Acad. Sci. (Paris) 262, 1016 (1966); F. Auzel,C. R. Acad. Sci. (Paris) 263, 819-821 (1966).
  20. V. V. Ovsyankin and P. P. Feofilov, “Cooperative sensitization of luminescence in crystals activated with rare earth ions,” Sov. Phys. JETP Lett. 4, 471-474 (1966). [Zh. Eksp. & Teor. Fiz. Pis'ma 4, 471-474 (1966)].
  21. R. H. Page, K. I. Schaffers, P. A. Waide, J. B. Tassano, S. A. Payne, W. F. Krupke, and W. K. Bischel, “Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium,” J. Opt. Soc. Am. B 15, 996-1008 (1998). [CrossRef]
  22. F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104, 139-174 (2004), and references therein. [CrossRef] [PubMed]
  23. D. Chen, Y. Wang, Y. Yu, P. Huang, and F. Weng, “Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission,” J. Solid State Chem. 181, 2763-2767 (2008). [CrossRef]
  24. Zh. Jin, Q. Nie, T. Xu, Sh. Dai, X. Shen, and X. Zhang, “Optical transitions and upconversion luminescence of Er3+/Yb3+, codoped lead-zinc-tellurite oxide glass,” Mater. Chem. Phys. 104, 62-67 (2007). [CrossRef]
  25. V. K. Rai, K. Kumar, and S. B. Rai, “Upconversion in Pr3+ doped tellurite glass,” Opt. Mater. 29, 873-878 (2007). [CrossRef]
  26. Q. Nie, L. Lu, T. Xu, Sh. Dai, X. Shen, X. Liang, X. Zhang, and X. Zhang, “Upconversion luminescence of Er3+/Yb3+-codoped natrium-germanium-bismuth glasses,” J. Phys. Chem. Solids 67, 2345-2350 (2006). [CrossRef]
  27. F. Auzel and D. Morin, French Patent B. F. N 96 13327, Procédé de fabrication de matériaux vitreux dopés et destinés à l'amplification optique ou laser, October 31, 1996.
  28. B. R. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750-761 (1962). [CrossRef]
  29. G. S. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511-520 (1962). [CrossRef]
  30. A. Kermaoui and F. Pellé, “Synthesis and infrared spectroscopic properties of Tm3+-doped phosphate glasses,” J. Alloys Compd. 469, 601-608 (2009). [CrossRef]
  31. Y. D. Huang, M. Mortier, and F. Auzel, “Stark level analysis for Er3+ -doped ZBLAN glass,” Opt. Mater. 17, 501-511 (2001). [CrossRef]
  32. D. L. Dexter and J. H. Schulman, “Theory of concentration quenching in inorganic phosphors,” J. Chem. Phys. 22, 1063-1070 (1954). [CrossRef]
  33. J. F. Suyver, J. Grimm, K. W. Krämer, and H. U. Güdel, “Highly-efficient near-infrared to visible upconversion process in NaYF4/Er3+,Yb3+,” J. Lumin. 114, 53-59 (2005). [CrossRef]
  34. S. E. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “New concept for efficient upconverter materials,” presented at the Journées Annuelles de la Société Française de Métallurgie et de Matériaux, Paris, France, 3-6 June 2008; Conference program, abstract I-3-27.
  35. S. E. Ivanova, A. M. Tkachuk, F. Pellé, M.-F. Joubert, Y. Guyot, and V. P. Gapontzev, “Energy transfer in RE-doped double fluoride crystals for diode pumped upconversion lasers,” presented at the 13th International Conference on Laser Optics, St. Petersburg, Russia, 23-28 June 2008, Technical program, p. ThR1-p64.
  36. F. Pellé, S. E. Ivanova, B. Viana, and A. M. Tkachuk, “Characterization of upconversion materials based on Er-Yb doped fluoride crystals,” presented at the 15th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter (ICL 2008), Lyon, France, 7-11 July 2008, Book of Abstracts, We-P-060, p. 494.
  37. S. Ivanova, F. Pellé, B. Viana, and A. Tkachuk, “IR to VIS upconversion in Er and Yb doped low phonon energy crystals: spectroscopic study and absolute efficiency measurements,” presented at the 3rd EPS-QEOD EUROPHOTON Conference on Solid-State, Fiber and Waveguided Light Sources, Paris, France, 2-5 September 2008, Conference Digest, THp13, p.46, Technical Digest on CD-ROM.
  38. S. I. Ivanova, F. Pellé, R. Esteban, M. Laroche, J. J. Greffet, S. Collin, J. L. Pelouard, and J. F. Guillemoles, “Thin film concepts for photon addition materials,” presented at the 23rd European Photovoltaic Solar Energy Conference and Exhibition, Valence, Spain, 1-5 September 2008, Conference program, abstract 1DV.2.56.
  39. Z. Pan, S. H. Morgan, K. Dyer, A. Ueda, and H. Liu, “Host-dependent optical transitions of Er3+ ions in lead-germanate and lead-tellurium-germanate glasses,” J. Appl. Phys. 79, 8906-8913 (1996). [CrossRef]
  40. R. S. Quimby, M. G. Drexhage, and M. J. Suscavage, “Efficient frequency up-conversion via energy transfer in fluoride glasses,” Electron. Lett. 23, 32-34 (1987). [CrossRef]
  41. F. Vetrone, J.-C. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “980 nm excited upconversion in an Er-doped ZnO-TeO2 glass,” Appl. Phys. Lett. 80, 1752-1754 (2002). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 
Fig. 4
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited