Abstract

Near vacuum ultraviolet (UV) upconversion (UC) emissions with a spectral resolution of 1 nm, from the 6GJ, 6DJ, 6IJ, 6PJ levels of Gd3+ and the 2L17/2, 4D7/2, 2H(2)9/2, 2D5/2, 4G7/2, 2K13/2, 2P3/2 levels of Er3+, were observed under 974 nm laser excitation. Mechanism analyses illustrate that successive energy transfers (ETs) from Yb3+ to Er3+ generate UV UC radiations in Er3+, while two resonant ETs from Er3+ to Gd3+ lead to UV UC radiations in Gd3+. Power dependence analyses indicate that the expected inefficient four- and five-photon processes have been switched into efficient two-photon processes due to a super saturation UC phenomenon that employs consecutive saturations at the intermediate states.

© 2009 OSA

1. Introduction

Continuous-wave (cw) ultraviolet (UV) lasers have found a number of promising applications such as: optical data storage, color displays, undersea communication, environmental monitoring, etc [13]. Upconversion (UC) pumping by means of the ladder-like energy levels in rare-earth ions can play a significant role for realizing such short-wavelength lasers, due to the ample availability of cost-effective high-power near infrared (NIR) diode lasers [1]. Efficient two-photon visible UC radiations have been extensively investigated in recent years [47], resulting in, e.g., the development of a room temperature cw green UC laser with an output power of 0.5 W [4]. However, high-order multi-photon UV UC radiations induced by NIR lasers have rarely been reported due to their inefficient generation mechanisms [812]. Switching of inefficient high-order multi-photon mechanisms into efficient two-photon mechanisms could have large impact in developing cw UV UC lasers and for extending UV UC emissions to even shorter wavelengths.

Decreasing the photon process can be realized by utilizing saturation effects induced via the intrinsic radiation characteristics of rare-earth ions in appropriate host lattices [13,14]. Usually, for a specific rare-earth ion, the higher the energy level is, the shorter the lifetime will be [15]. Long-lived intermediate excited states can thereby become energy reservoirs and function similarly to the ground state when populating higher energy levels. This merit can allow populating rare-earth ions’ excited energy levels through a series of saturation at the intermediate states. These consecutive saturations of intermediates can decrease the effective photon processes and transfer most of the absorbed energy to the highest energy level, resulting in a two-photon sensitization mechanism which populates the highest energy level. Such super saturation (SS) UC process can be utilized for achieving UV lasers, since it offers a novel way to allow efficient pumping via the use of cost-effective high-power NIR diode lasers. Although the sensitized SSUC effect has been theoretically discussed in Ref. 14, however, its importance for UV UC lasers and their experimental realization in near vacuum UV range has not been reported so far. In this letter, we report on SSUC processes for generating near vacuum UV UC radiations in Er3+ and Gd3+ ions under 974-nm diode laser excitation.

NaGdF4 is known to be one of the most efficient host materials for UC emissions, since it has low nonradiative losses due to a low phonon cutoff energy of about 400 cm−1 [16]. Trivalent Gd3+ ions have large energy gaps, e.g., of about 32000 cm−1 between the first excited 6P7/2 state and the ground state [10,17]. These characteristics determine the long lifetimes of the Gd3+ ions’ excited states, e.g., about 10 ms for the 6P7/2(Gd) state in a single NaGdF4 crystal [18]. Trivalent Er3+ ions have several energy levels that overlap with the Gd3+ ions, e.g., the 2P3/2, 2K13/2, and 2D5/2 states have similar energy to the 6P7/2(Gd) state [19,20]. The strong coupling between Er3+ and Gd3+ enables the generation of common long-lived states or the accommodation of large populations produced via the SSUC process in the long-lived reservoir states of high Gd3+ ions. Therefore, it is challenging to investigate near vacuum UV UC radiations in Yb3+/Er3+-codoped NaGdF4 microcrystals.

2. Experimental

NaGdF4 (NaYF4) powders doped with 2 mol% Er3+ and 20 mol% Yb3+ ions were synthesized by a co-precipitation method [21], through annealing at 600 °C for 5 h in air. Details for the measurement of room temperature UC fluorescence have been presented in our previous work [22]. In the present work a Hamamatsu R7154 photomultiplier tube was employed to detect the UV UC radiations due to its sensitive wavelength range of 160-320 nm. X-ray diffraction experiments evidenced that the prepared NaGdF4 (NaYF4) powders have a hexagonal crystal structure, and transmission electron microscopy showed that the obtained powders had a size range of 200-500 nm.

3. Results and discussions

3.1. Near vacuum UV UC radiations of Er3+ and Gd3+ ions

Figure 1 displays UV UC radiation recordings (with a relatively high resolution of 1 nm) of (a) NaGdF4 and (b) NaYF4 powders under 974 nm diode laser excitation of 37 W/cm2. Figure 1(a) shows four bands centered at 245.8, 252.3, 275.8, and 311.1 nm corresponding to transitions from 6D5/2,7/2, 6D9/2, 6IJ, and 6PJ to the ground 8S7/2 state of Gd3+ ions, respectively [23]. The sharp peaks in these bands have been assigned to the J sub levels of Gd3+ ions. Figure 1(b) displays the seven measured UV UC bands centered at 242.9, 254.6, 274.4, 284.2, 289.2, 303.3, and 316.1 nm, which correspond in order to the Er3+ ions’ transitions from 2L17/2, 4D7/2, 2H(2)9/2, 2D5/2, 4G7/2, 2K13/2, and 2P3/2 to the ground 4I15/2 state, respectively [20,24]. Comparison between Figs. 1(a) and (b) illustrates that the peaks marked by asterisks at 242.9, 254.6, and 316.1 nm in Fig. 1(a) arise from Er3+ ions’ UV UC emissions, and that the UV UC radiations in NaGdF4:Yb3+/Er3+ powders are about two orders of magnitude higher than those of the NaYF4:Yb3+/Er3+ powders. The inset in Fig. 1 is an extension of Fig. 1(a) towards shorter wavelengths. As can be seen, the shortest fluorescent bands that upconverted from the cw NIR light were observed at 191 and 202 nm, which correspond to 6G13/28S7/2 and 6GJ8S7/2 (J = 3/2, 5/2, 7/2, 9/2, 11/2) in the Gd3+ ions, respectively.

 

Fig. 1 Recorded UV UC radiation spectrum of (a) NaGdF4 and (b) NaYF4 microcrystals doped with 20 mol%Yb3+, 2 mol% Er3+ ions in the wavelength range 230-330 nm. The inset is an extended recording of Fig. 1(a) in the spectroscopic range of 185-230 nm.

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3.2. Mechanisms for near vacuum UV UC radiations of Er3+and Gd3+ ions

The energy level diagrams of Er3+, Yb3+, and Gd3+ ions as well as the proposed UC mechanisms are depicted in Fig. 2 . Regarding NaYF4:Yb3+/Er3+, the 4G11/2 and 2H9/2 states emitting 390 and 410 nm radiations are populated by three energy transfers (ETs) from excited Yb3+ ions, employing two alternative UC pathways [25,26]. Subsequently, two other ETs from Yb3+ ions can excite Er3+ ions from the 4G11/2 and 2H9/2 to the 2H(2)9/2 and 2D5/2 states (with an energy mismatch of about 310 cm−1 and 211 cm−1), generating radiations at 274.4 and 284.2 nm, respectively. Cascading nonradiative relaxations can then populate in order the 4G7/2, 2K13/2, and 2P3/2 states where 289.2, 303.3, and 316.1 nm UV UC radiations arise, respectively. Additionally, Er3+ ions in the 2P3/2 state can be excited to the 2L17/2 state by another ET from the 2F5/2(Yb) state (with an energy mismatch of about 254 cm−1), followed by nonradiative relaxations to the 4D7/2 state. UV UC emissions at 242.9 and 254.6 nm were then generated by transitions from the 2L17/2 and 4D7/2 to the ground state, respectively. It should be noted that four-photon UC processes are involved to populate the 2H(2)9/2, 2D5/2, 4G7/2, 2K13/2, and 2P3/2 states, while five-photon UC processes are involved to populate the 2L17/2 and 4D7/2 states.

 

Fig. 2 Energy level diagrams of Er3+, Yb3+, and Gd3+ ions as well as the proposed mechanisms to produce UV UC radiations.

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As for the NaGdF4:Yb3+/Er3+ powders, 6IJ(Gd) states can be populated by an efficient ET 2 process from the 2H(2)9/2 state of Er3+ ions with an energy mismatch of about 122 cm−1, whereas 6PJ(Gd) states can be populated by an efficient ET 1 process from the 4D5/2, 4G7/2, and 2K13/2 states of Er3+ ions (The energy mismatch is 1673 cm−1, 859 cm−1, and 196 cm−1, respectively). Nonradiative relaxations from the 6IJ(Gd) state can also populate the 6PJ(Gd) state with the energy of about 2560 cm−1 lower [10]. Decays from the 6PJ(Gd) and 6IJ(Gd) states to the ground state can then generate UV UC radiations at 311.1 and 275.8 nm, respectively. Subsequently, two ETs from Yb3+ ions can promote Gd3+ ions in the 6PJ state consecutively to the 6DJ and 6GJ states, which generate UV UC radiations at 245.8 and 200 nm, respectively. It should be noted that, due to the dominated resonant ET 1 and ET 2 processes, the populations in 6PJ and 6IJ of Gd3+ ions should be proportional to the populations in the 2K13/2 and 2D5/2 of Er3+ ions, respectively. Thus, the 6PJ(Gd) and 6IJ(Gd) states involve four-photon UC mechanisms, while the 6DJ(Gd) and 6GJ(Gd) states involve five- and six-photon UC processes, respectively.

3.4. Analysis on comparison results of near vacuum UV UC in NaYF4:Yb3+/Er3+ and NaGdF4:Yb3+/Er3+ powders

The observed two orders higher UV UC radiation efficiency of the NaGdF4 compared to NaYF4 might arise from the strong coupling between the Er3+ and Gd3+ ions bridged over by ETs 1 and 2. It is found that the Er3+ ions have similar visible and NIR radiation parameters in NaGdF4 and NaYF4 lattices due to their similar properties (unpublished data), leading expectedly to similar magnitudes of the UV UC radiations. This contradiction might derive from the fact that the previous dynamic equilibrium in Yb3+/Er3+-codoped NaYF4 is destroyed by ETs 1 and 2 which transfer nearly all the UV populations from lower excited Er3+ to higher excited Gd3+ ions. To establish a new dynamic equilibrium in the Er3+ ions, a large population from the lower energy levels needs to be transferred up by excitation, which seems as if the Yb3+/Er3+ system is being exerted to an ‘upconverting force’ by the Gd3+ ions. Similarly, this can induce a series of similar results in the intermediate states and thus increase their UC rates, leading together with their low losses to a series of saturations in these intermediate states. This conclusion has been verified by direct observations of a reduction of slope n values at the green, red, 390-nm and 409-nm UC radiations in NaGdF4:Yb3+/Er3+ powders as compared to that in NaYF4:Yb3+/Er3+ powders.

Efficient ETs 1 and 2 from lower Er3+ to much higher Gd3+ ions can cause the extinction of UV UC radiations from the 2H(2)9/2, 4D5/2, 4G7/2, 2K13/2 levels of Er3+ ions, as displayed in Fig. 1(a). The observed UV UC radiation from the 2P3/2(Er) state in NaGdF4 arises from the energy back transfer (EBT 1) from the 6PJ(Gd) to 2P3/2(Er) state that has 500 cm−1 lower energy [17]. The weaker UC fluorescent intensity of the 2P3/2(Er) than 6PJ(Gd) state derives from the fact that Er3+ ions are about 40 times lower than Gd3+ ions and both states have the same radiation rate due to their strong coupling (unpublished data). Population of the 2P3/2(Er) state by EBT 1 can lead to the population of the 2L17/2(Er) and 4D7/2(Er) states, which generates the 242.9 and 254.6 nm UV UC radiations marked by asterisks in Fig. 1(a). The EBT 2 process from the 6DJ(Gd) states may also play a role for populating the 4D7/2(Er) state.

3.5. Demonstration of SSUC mechanism in NaGdF4:Yb3+/Er3+ powders

Figure 3 shows the pump power dependences of all radiations in the NaGdF4:Yb3+/Er3+ powders. The number of photons required to populate the upper emitting state can be obtained by the relation IfPn, where If is the fluorescent intensity, P is the pump laser power, and n is the number of the laser photons required [9]. As illustrated in Fig. 3, n ≈2 is observed for 276- and 311-nm four-photon, and 252-nm five-photon UV UC radiations at such low pumping powers as 14-42 W/cm2. This demonstrates the occurrence of a SSUC phenomenon for generation of the UV radiations. It is also noted from Fig. 3 that all the intermediate states (emitting red, green, 409- and 390-nm radiations) have the same value of n = 1 as the 2F5/2(Yb) state (emitting 1000-nm radiation). This suggests that the SSUC mechanism is induced by consecutive saturations at the intermediate states, illustrating clearly that the UC rate in any intermediate state is much larger than its corresponding decay rates [14]. Therefore, it can be perceived that all the intermediate states function as a series of “railway stations” for “upconverted population trains”, finally leading to the occurrence of the SSUC phenomenon. The almost zero value of n = 0.3 arises from the saturation of the 4I13/2(Er) state [27,28].

 

Fig. 3 Pump power dependences of all fluorescent radiations (>250 nm) in the NaGdF4:Yb3+/Er3+ powders.

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4.Conclusions

In summary, we have demonstrated the occurrence of a SSUC mechanism for generating near vacuum UV emissions in Gd3+ and Er3+ ions under 974 nm cw excitation. A series of ETs from the Yb3+ ions, inducing consecutive saturations in Er3+ ion’s intermediate states, lead to UV UC radiations in Er3+ ions, while two resonant ETs from Er3+ to Gd3+ ions evoke UV UC radiations of Gd3+ ions. It is found that the SSUC can switch inefficient four- and five-photon processes into efficient two-photon process, offering a novel efficient way to pump cw UV UC lasers with NIR light.

Acknowledgement

This work was supported by the SIDA Asian-Swedish Research Partnership Programme, and the 863 Hi-Tech Research and Development Program of the People’s Republic of China.

References and links

1. F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104(1), 139–174 (2004). [CrossRef]   [PubMed]  

2. D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007). [CrossRef]  

3. L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007). [CrossRef]  

4. J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005). [CrossRef]  

5. E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006). [CrossRef]  

6. F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004). [CrossRef]  

7. E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008). [CrossRef]  

8. L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997). [CrossRef]  

9. F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005). [CrossRef]  

10. C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. D. Wei, G. F. Wang, R. Kim, and L. L. Wang, “Ultraviolet upconversion emissions of Gd3+.,” Opt. Lett. 33(8), 857–859 (2008). [CrossRef]   [PubMed]  

11. X. B. Chen and Z. F. Song, “Study on six-photon and five-photon ultraviolet upconversion luminescence,” J. Opt. Soc. Am. B 24(4), 965–971 (2007). [CrossRef]  

12. G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007). [CrossRef]  

13. M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000). [CrossRef]  

14. J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005). [CrossRef]  

15. M. J. Weber, “Radiative and multiphonon relaxation of rare-earth ions in Y2O3,” Phys. Rev. 171(2), 283–291 (1968). [CrossRef]  

16. A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005). [CrossRef]  

17. W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968). [CrossRef]  

18. H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003). [CrossRef]  

19. W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968). [CrossRef]  

20. J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006). [CrossRef]  

21. G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004). [CrossRef]  

22. G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008). [CrossRef]  

23. E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008). [CrossRef]  

24. H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002). [CrossRef]  

25. G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002). [CrossRef]  

26. G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007). [CrossRef]  

27. G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007). [CrossRef]  

28. R. H. Page, K. I. Schaffers, P. A. Waide, J. B. Tassano, S. A. Payne, W. F. Krupke, and W. K. Bischel, “Upconversion-pulmped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium,” J. Opt. Soc. Am. B 15(3), 996–1008 (1998). [CrossRef]  

References

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  1. F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104(1), 139–174 (2004).
    [Crossref] [PubMed]
  2. D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
    [Crossref]
  3. L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
    [Crossref]
  4. J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
    [Crossref]
  5. E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
    [Crossref]
  6. F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
    [Crossref]
  7. E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
    [Crossref]
  8. L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
    [Crossref]
  9. F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
    [Crossref]
  10. C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. D. Wei, G. F. Wang, R. Kim, and L. L. Wang, “Ultraviolet upconversion emissions of Gd3+.,” Opt. Lett. 33(8), 857–859 (2008).
    [Crossref] [PubMed]
  11. X. B. Chen and Z. F. Song, “Study on six-photon and five-photon ultraviolet upconversion luminescence,” J. Opt. Soc. Am. B 24(4), 965–971 (2007).
    [Crossref]
  12. G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
    [Crossref]
  13. M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
    [Crossref]
  14. J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
    [Crossref]
  15. M. J. Weber, “Radiative and multiphonon relaxation of rare-earth ions in Y2O3,” Phys. Rev. 171(2), 283–291 (1968).
    [Crossref]
  16. A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
    [Crossref]
  17. W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
    [Crossref]
  18. H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
    [Crossref]
  19. W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
    [Crossref]
  20. J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
    [Crossref]
  21. G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
    [Crossref]
  22. G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
    [Crossref]
  23. E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
    [Crossref]
  24. H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002).
    [Crossref]
  25. G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
    [Crossref]
  26. G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
    [Crossref]
  27. G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
    [Crossref]
  28. R. H. Page, K. I. Schaffers, P. A. Waide, J. B. Tassano, S. A. Payne, W. F. Krupke, and W. K. Bischel, “Upconversion-pulmped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium,” J. Opt. Soc. Am. B 15(3), 996–1008 (1998).
    [Crossref]

2008 (4)

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. D. Wei, G. F. Wang, R. Kim, and L. L. Wang, “Ultraviolet upconversion emissions of Gd3+.,” Opt. Lett. 33(8), 857–859 (2008).
[Crossref] [PubMed]

2007 (6)

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

X. B. Chen and Z. F. Song, “Study on six-photon and five-photon ultraviolet upconversion luminescence,” J. Opt. Soc. Am. B 24(4), 965–971 (2007).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

2006 (2)

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

2005 (4)

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

2004 (3)

F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104(1), 139–174 (2004).
[Crossref] [PubMed]

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

2003 (1)

H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
[Crossref]

2002 (2)

H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002).
[Crossref]

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

2000 (1)

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

1998 (1)

1997 (1)

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

1968 (3)

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
[Crossref]

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
[Crossref]

M. J. Weber, “Radiative and multiphonon relaxation of rare-earth ions in Y2O3,” Phys. Rev. 171(2), 283–291 (1968).
[Crossref]

Aebischer, A.

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Aegerter, M. A.

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

Aghahadi, B.

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

Angeles-Chavez, C.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Arai, Y.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Auzel, F.

F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104(1), 139–174 (2004).
[Crossref] [PubMed]

Bär, S.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Bettinelli, M.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

Biner, D.

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Bischel, W. K.

Boyer, J.

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

Boyer, J. C.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

Butterworth, S.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Cao, C. Y.

Capobianco, J. A.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

Carnall, W. T.

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
[Crossref]

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
[Crossref]

Chen, B. J.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Chen, D. P.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Chen, D. Q.

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

Chen, G. Y.

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

Chen, X. B.

de Araújo, C. B.

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

de la Rosa, E.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Díaz-Torres, L. A.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Diening, A.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Dorenbos, P.

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

Fields, P. R.

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
[Crossref]

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
[Crossref]

Gamelin, D. R.

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

García-Revilla, S.

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

Ge, Y.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Gerner, P.

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Grimm, J.

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Güdel, H. U.

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

Guo, L. H.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Haase, M.

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

Hashimoto, S.

H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
[Crossref]

Heer, S.

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Hehlen, M. P.

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

Heumann, E.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Hirai, T.

H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
[Crossref]

Huang, L. H.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Huang, P.

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

Huang, S. H.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Huber, G.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Jiang, Z. K.

H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002).
[Crossref]

Jose, R.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Kim, R.

Kondo, H.

H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
[Crossref]

Krämer, K.

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

Krämer, K. W.

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Krupke, W. F.

Liang, H. J.

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

Liu, H. C.

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

Liu, Y.

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

Lu, H. C.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Lu, S. Z.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Lüthi, S. R.

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

Maciel, G. S

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

Menezes, L. de S.

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

Messaddeq, Y.

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

Meza, O.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Naccache, R.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

Ohishi, Y.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Page, R. H.

Pandozzi, F.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

Payne, S. A.

Pollau, M.

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

Qin, G. S.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Qin, W. P.

C. Y. Cao, W. P. Qin, J. S. Zhang, Y. Wang, P. F. Zhu, G. D. Wei, G. F. Wang, R. Kim, and L. L. Wang, “Ultraviolet upconversion emissions of Gd3+.,” Opt. Lett. 33(8), 857–859 (2008).
[Crossref] [PubMed]

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Rademaker, K.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
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Rajnak, K.

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
[Crossref]

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
[Crossref]

Reinhard, C.

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Salas, P.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Schaffers, K. I.

Seelert, W.

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

Shulin, E.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Solis, D.

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

Somesfalean, G.

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

Song, Z. F.

Speghini, A.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

Sun, Q.

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

Suyer, J. F.

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Suyver, J. F.

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

Suzuki, T.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Tassano, J. B.

van der Kolk, E.

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

Van Veen, M. K.

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

Vetrone, F.

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

Waide, P. A.

Wang, F. P.

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

Wang, G. F.

Wang, L. L.

Wang, Y.

Wang, Y. S.

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

Weber, M. J.

M. J. Weber, “Radiative and multiphonon relaxation of rare-earth ions in Y2O3,” Phys. Rev. 171(2), 283–291 (1968).
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Wei, G. D.

Wu, C. F.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Xu, H. L.

H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002).
[Crossref]

Yamashita, T.

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

Yang, W. J.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Yi, G. S.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Yu, Y. L.

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

Zhang, J. S.

Zhang, Z. G.

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

G. Y. Chen, G. Somesfalean, Z. G. Zhang, Q. Sun, and F. P. Wang, “Ultraviolet upconversion fluorescence in rare-earth-ion-doped Y2O3 induced by infrared diode laser excitation,” Opt. Lett. 32(1), 87–89 (2007).
[Crossref]

Zhao, D.

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

Zhao, S. Y.

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Zhu, P. F.

Appl. Phys. Lett. (4)

D. Q. Chen, Y. S. Wang, Y. L. Yu, and P. Huang, “Intense ultraviolet upconversion luminescence from Tm3+/Yb3+:β-YF3 nanocrystals embedded glass ceramic,” Appl. Phys. Lett. 91(5), 051920 (2007).
[Crossref]

L. H. Huang, T. Yamashita, R. Jose, Y. Arai, T. Suzuki, and Y. Ohishi, “Intense ultraviolet emission from Tb3+ and Yb3+ codoped glass ceramic containing CaF2 nanocrystals,” Appl. Phys. Lett. 90(13), 131116 (2007).
[Crossref]

E. Heumann, S. Bär, K. Rademaker, G. Huber, S. Butterworth, A. Diening, and W. Seelert, “Semiconductor-laser-pumped high-power upconversion laser,” Appl. Phys. Lett. 88(6), 061108 (2006).
[Crossref]

L. de S. Menezes and C. B. de Araújo,G. S Maciel, Y. Messaddeq, and M. A. Aegerter, “Continuous wave ultraviolet frequency upconversion due to triads of Nd3+ ions in fluoroindate glass,” Appl. Phys. Lett. 70, 683–685 (1997).
[Crossref]

Chem. Phys. Lett. (2)

A. Aebischer, S. Heer, D. Biner, K. Krämer, M. Haase, and H. U. Güdel, “Visible light emission upon near-infrared excitation in a transparent solution of nanocrystalline β-NaGdF4:Yb3+,Er3+,” Chem. Phys. Lett. 407(1-3), 124–128 (2005).
[Crossref]

G. Y. Chen, Y. Liu, Z. G. Zhang, B. Aghahadi, G. Somesfalean, Q. Sun, and F. P. Wang, “Four-photon upconversion induced by infrared diode laser exciation in rare-earth-ion-doped Y2O3 nanocrystals,” Chem. Phys. Lett. 448(1-3), 127–131 (2007).
[Crossref]

Chem. Rev. (1)

F. Auzel, “Upconversion and anti-Stokes processes with f and d ions in solids,” Chem. Rev. 104(1), 139–174 (2004).
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J. Appl. Phys. (3)

F. Vetrone, J. Boyer, J. A. Capobianco, A. Speghini, and M. Bettinelli, “Significance of Yb3+ concentration on the upconversion mechanisms in codoped Y2O3:Er3+, Yb3+ nanocrystals,” J. Appl. Phys. 96(1), 661–667 (2004).
[Crossref]

E. de la Rosa, D. Solis, L. A. Díaz-Torres, P. Salas, C. Angeles-Chavez, and O. Meza, “Blue-green upconversion emission in ZrO2:Yb3+ nanocrystals,” J. Appl. Phys. 104(10), 103508 (2008).
[Crossref]

G. S. Qin, W. P. Qin, S. H. Huang, C. F. Wu, D. Zhao, B. J. Chen, S. Z. Lu, and E. Shulin, “Infrared-to-violet upconversion from Yb3+ and Er3+ codoped amorphous fluoride film prepared by pulsed laser deposition,” J. Appl. Phys. 92(11), 6936–6938 (2002).
[Crossref]

J. Chem. Phys. (2)

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic Energy levels of the trivalent lanthanide aquo ions. II. Gd3+,” J. Chem. Phys. 49(10), 4443–4446 (1968).
[Crossref]

W. T. Carnall, P. R. Fields, and K. Rajnak, “Electronic energy levels in the trivalent lanthanide quo ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+,” J. Chem. Phys. 49(10), 4424 (1968).
[Crossref]

J. Lumin. (2)

J. F. Suyer, J. Grimm, M. K. Van Veen, D. Biner, K. W. Krämer, and H. U. Güdel, “Upconversion spectroscopy and properties of NaYF4 doped with Er3+, Tm3+ and/ or Yb3+,” J. Lumin. 117(1), 1–12 (2006).
[Crossref]

H. Kondo, T. Hirai, and S. Hashimoto, “Energy migration and relaxation through Gd3+ sublattice in NaGdF4,” J. Lumin. 102–103, 727–732 (2003).
[Crossref]

J. Opt. Soc. Am. B (2)

J. Phys. Chem. B (1)

F. Pandozzi, F. Vetrone, J. C. Boyer, R. Naccache, J. A. Capobianco, A. Speghini, and M. Bettinelli, “A spectroscopic analysis of blue and ultraviolet upconverted emissions from Gd3Ga5O12:Tm3+, Yb3+ nanocrystals,” J. Phys. Chem. B 109(37), 17400–17405 (2005).
[Crossref]

J. Phys. Chem. C (1)

G. Y. Chen, H. C. Liu, H. J. Liang, G. Somesfalean, and Z. G. Zhang, “Upconversion emission enhancement in Yb3+/Er3+-codoped Y2O3 nanocrystals by tridoping with Li+ ions,” J. Phys. Chem. C 112(31), 12030–12036 (2008).
[Crossref]

Nano Lett. (1)

G. S. Yi, H. C. Lu, S. Y. Zhao, Y. Ge, W. J. Yang, D. P. Chen, and L. H. Guo, “Synthesis, characterization, and biological application of size-controlled nanocrystalline NaYF4:Yb,Er infrared-to-visible upconversion phosphors,” Nano Lett. 4(11), 2191–2196 (2004).
[Crossref]

Opt. Lett. (2)

Opt. Mater. (1)

J. F. Suyer, A. Aebischer, D. Biner, P. Gerner, J. Grimm, S. Heer, K. W. Krämer, C. Reinhard, and H. U. Güdel, “Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion,” Opt. Mater. 27(6), 1111–1130 (2005).
[Crossref]

Phys. Rev. (1)

M. J. Weber, “Radiative and multiphonon relaxation of rare-earth ions in Y2O3,” Phys. Rev. 171(2), 283–291 (1968).
[Crossref]

Phys. Rev. B (5)

M. Pollau, D. R. Gamelin, S. R. Lüthi, H. U. Güdel, and M. P. Hehlen, “Power dependence of upconversion luminescence in lanthanide and transition-metal-ion systems,” Phys. Rev. B 61(5), 3337–3346 (2000).
[Crossref]

J. F. Suyver, A. Aebischer, S. García-Revilla, P. Gerner, and H. U. Güdel, “Anomalous power dependence of sensitized upconversion luminescence,” Phys. Rev. B 71(12), 125123 (2005).
[Crossref]

E. van der Kolk, P. Dorenbos, K. Krämer, D. Biner, and H. U. Güdel, “High-resolution luminescence spectroscopy study of down-conversion routes in NaGdF4:Nd3+ and NaGdF4:Tm3+ using synchrotron radiation,” Phys. Rev. B 77(12), 125110 (2008).
[Crossref]

H. L. Xu and Z. K. Jiang, “Ultraviolet and violet upconversion luminescence in Er3+-doped yttrium aluminum garnet crystals,” Phys. Rev. B 66(3), 035103 (2002).
[Crossref]

G. Y. Chen, G. Somesfalean, Y. Liu, Z. G. Zhang, Q. Sun, and F. P. Wang, “Upconversion mechanism for two-color emission in rare-earth-ion-doped ZrO2 nanocrystals,” Phys. Rev. B 75(19), 195204 (2007).
[Crossref]

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Figures (3)

Fig. 1
Fig. 1

Recorded UV UC radiation spectrum of (a) NaGdF4 and (b) NaYF4 microcrystals doped with 20 mol%Yb3+, 2 mol% Er3+ ions in the wavelength range 230-330 nm. The inset is an extended recording of Fig. 1(a) in the spectroscopic range of 185-230 nm.

Fig. 2
Fig. 2

Energy level diagrams of Er3+, Yb3+, and Gd3+ ions as well as the proposed mechanisms to produce UV UC radiations.

Fig. 3
Fig. 3

Pump power dependences of all fluorescent radiations (>250 nm) in the NaGdF4:Yb3+/Er3+ powders.

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