Optical characterization of Er3+and Yb3+ co-doped barium ...

More documents

Recommendations

Info

elaxation rate WET can be written as [43] WETp 1 R 6 pN DA 2 , ð5Þ where N is the ionic concentration. Since the Er 3 þ 3 þ and Yb concentration on the present sample is too low compared to that reported in the literature [24,44], ET does not have appreciable influence on the non-radiative losses. The values of WOH can be determined from the quantitative measurements of the OH content and the low frequency vibrational modes in the sample from the infrared vibrational spectrum shown in Fig. 7. The FTIR spectrum shows the characteristic Te–O symmetric vibration at 640 cm 1 , which is usually present in the tellurite glass [45]. Using this frequency, the transition rate for multiphonon vibrational loss (Wmp) of the 1571 nm emission band was estimated to be 0.00282 s 1 [42], which is negligibly small. So the main contribution is coming from water content, which is confirmed by the absorption band at 2933 cm 1 in the IR spectrum. In the tellurite glasses, these absorption bands originate from the stretching vibration of OH groups, which are incorporated as Te(OH) 6 and H2TeO6 [45–47], and the 2283 cm 1 absorption are ascribed to the strongly hydrogen-bonded OH-groups. Because of the various sites of OH-groups in the vitreous host and the highly disordered hydrogen-bonded OH-groups made the absorption bands quite broad. The absolute measurement of OH content in glasses is difficult, particularly at concentration below 1000 ppm. However, a relative estimate of the water content can be obtained from the infrared absorption measurements corresponding to the OH band. The amount of water content in the glass samples can be obtained from the measurement of the absorption coefficient at the OH peak of the IR spectrum and is estimated to be nearly 2.4 cm 1 .AnOH concentration of 3607100 ppm gives absorption of 2.8 cm 1 [48]. By comparison, the corresponding water content was estimated to be 308 ppm (5.5 10 19 molecules/cm 3 ). Since the second order vibrational frequency of OH is almost in resonance with the 4 113/2- 4 I15/2 transition in Er 3þ , they are powerful quenchers of the Er 3þ emission at 1571 nm. The quenching rate due to this water content is found to be proportional to the absorption coefficient of the OH radicals [49]. ThemajorsourcesofOHcontentintheglassarefromthestarting chemicals as well as from the synthesis atmosphere. Higher level of water content can be suppressed using moisture free chemicals melted in water free environment as well as by re-melting of the glasses. The internal quantum efficiency, (ZInt) can be evaluated from the ratio of the fluorescence to radiative decay time [26]. The Absorbance 4 3 2 1 0 Te-O O-H 1000 2000 3000 4000 Frequency (cm -1 ) Te(OH) 6 Fig. 7. Infrared vibration spectrum of glass composition showing the presence of OH radicals associated with the tellurite network. M. Pokhrel et al. / Journal of Luminescence 132 (2012) 1910–1916 1915 Upconversion efficiency (%) 0.300 0.225 0.150 0.075 lifetime obtained for the 1571 nm emission in the glass composition was 2.693 ms and this together with the calculated radiative decay time of 3.707 ms yields a radiative internal quantum efficiency of near 73%. It should be noted that this internal quantum yield is smaller compared to similar reported tellurite composition [17,21,27,33]. However the influence of OH radicals and other non-radiative interactions from Er 3 þ ions detracts the efficiency less than 100% as noticed from our calculations. The upconversion efficiency (Zup) can be calculated by comparing the upconversion luminescence signal with the directly excited signal intensity using the expression [50] P Z ¼ Z absð488nmÞI550ð980nmÞ q Pabsð980nmÞI550ð488nmÞ where Pabs(l) represent the power absorbed by the glass sample at the indicated wavelength, and I 550(l) denotes the relative intensity generated in the green when the sample is photo excited at the indicated pump wavelength, and Zq represents the internal radiative quantum yield of the 547 nm emission. For the 4 S3/2 state of Er 3 þ , tflu and trad were determined to be 26 ms and 0.260 ms respectively yielding an internal radiative quantum yield of 10% for the green upconversion emission. The values of P abs(l) in Eq. (6) were calculated from the measured power incident on the sample, and the known absorption coefficient at the excitation wavelength. On the basis of Eq. (6), the 980 nm- 547 nm upconversion efficiency in glass has been calculated from experimental measurements made for several values of excitation power at 980 nm, 488 nm and the results are illustrated in Fig. 8. For all the pump powers, Z increases approximately linearly with an efficiency of 0.3% at 60 mW excitation. The saturation of the detector limits the efficiency measurements for higher values of the excitation power. 4. Conclusion 10 20 30 40 50 60 Excitation Power (mW) Fig. 8. Green upconversion efficiency dependence under 980 nm excitation power. An in depth spectroscopic analysis of Yb 3 þ /Er 3 þ co-doped (Ba,La) tellurite glass host has been performed following the theoretical and experimental methods. The investigations on the fluorescence spectral properties of Yb 3 þ /Er 3 þ co-doped (Ba,La) tellurite glass composition shows better optical performance in terms of gain cross section and full width at half max (FWHM) of over 91 nm compared to other glass system. Although, the internal quantum efficiency of the present system approaches near 73% that is comparable to similar compositions, the influence of non-radiative interactions from OH radicals can be ð6Þ
1916 suppressed using moisture free chemical melting in water free environment or by re-melting the glass and increase the internal efficiency close to100%. The internal radiative quantum yield of 10% was obtained for the green upconversion emission at 547 nm. The low upconversion efficiency offers additional possibility of enhancing the infrared emission quantum yield by optimizing the dopant concentration as well as synthesizing the sample in moisture free environment. More detailed investigations on range of Yb 3 þ /Er 3 þ dopant concentrations are under way to understand the details of the energy transfer and other non-radiative process. Acknowledgments This research was supported by the National Science Foundation Partnership for Research and Education in Materials (NSF-PREM) Grant no. DMR-0934218. One of the authors, Balaji, also acknowledges the support from the Director, CSIR-CGCRI, Kolkata. References [1] A. Brenier, Chem. Phys. Lett. 290 (1998) 329. [2] Y. Chen, Y. Huang, Z. Luo, Chem. Phys. Lett. 382 (2003) 481. [3] N. Chiodini, A. Paleari, G. Brambilla, E.R. Taylor, Appl. Phys. Lett. 80 (2002) 4449. [4] D.F. de Sousa, L.F.C. Zonetti, M.J.V. Bell, R. Lebullenger, A.C. Hernandes, L.A.O. Nunes, J. Appl. Phys. 85 (1999) 2502. [5] D. Jaque, J. Capmany, F. Molero, Z.D. Luo, J. García Sole, Opt. Mater. 10 (1998) 211. [6] N. Rakov, F.E. Ramos, G. Hirata, M. Xiao, Appl. Phys. Lett. 83 (2003) 272. [7] T.J. Whitley, C.A. Millar, R. Wyatt, M.C. Brierley, D. Szebesta, Electron. Lett. 27 (1991) 1785. [8] Y.C. Yan, A.J. Faber, H. de Waal, P.G. Kik, A. Polman, Appl. Phys. Lett. 71 (1997) 2922. [9] Y. Hu, S. Jiang, G. Sorbello, T. Luo, Y. Ding, B.-C. Hwang, J.-H. Kim, H.-J. Seo, N. Peyghambarian, J. Opt. Soc. Am. A 18 (2001) 1928. [10] H. Lin, G. Meredith, S. Jiang, X. Peng, T. Luo, N. Peyghambarian, E.Y.-B. Pun, J. Appl. Phys. 93 (2003) 186. [11] P.C. Becker, N.A. Olsson, J.R. Simpson, Erbium-Doped Fiber Amplifiers Fundamentals and Technology, Academic Press, San Diego, 1999. [12] J.C. Michel, D. Morin, F. Auzel, Rev. Phys. Appl. 13 (1978) 859. [13] Z. Pan, S.H. Morgan, K. Dyer, A. Ueda, H. Liu, J. Appl. Phys. 79 (1996) 8906. [14] K.J. Pluciński, W. Gruhn, J. Wasylak, J. Ebothe, D. Dorosz, J. Kucharski, I.V. Kityk, Opt. Mater. 22 (2003) 13. [15] H. Sun, S. Xu, S. Dai, J. Zhang, L. Hu, Z. Jiang, Solid State Commun. 132 (2004) 193. [16] X. Wang, H. Lin, D. Yang, L. Lin, E.Y.-B. Pun, J. Appl. Phys. 101 (2007) 113535. [17] J. Yang, L. Zhang, L. Wen, S. Dai, L. Hu, Z. Jiang, J. Appl. Phys. 95 (2004) 3020. M. Pokhrel et al. / Journal of Luminescence 132 (2012) 1910–1916 [18] M.A.P. Silva, Y. Messaddeq, V. Briois, M. Poulain, F. Villain, S.J.L. Ribeiro, J. Phys. Chem. Solids 63 (2002) 605. [19] J. Lu, M. Prabhu, J. Song, C. Li, J. Xu, K. Ueda, A.A. Kaminskii, H. Yagi, T. Yanagitani, Appl. Phys. B Lasers Opt. 71 (2000) 469. [20] A. Ghosh, R. Debnath, Opt. Mater. 31 (2009) 604. [21] I. Jlassi, H. Elhouichet, M. Ferid, C. Barthou, J. Lumin. 130 (2010) 2394. [22] B.R. Judd, Phys. Rev. 127 (1962) 750. [23] G. Ofelt, J. Chem. Phys. 37 (1962) 511. [24] M. Pokhrel, G.A. Kumar, P. Samuel, K.I. Ueda, T. Yanagitani, H. Yagi, D.K. Sardar, Opt. Mater. Express 1 (2011) 1272. [25] A.A. Kaminskii, Laser Crystals: Physics and Properties, Springer-Verlag, Berlin, New York, 1979. [26] A.A. Kaminskii, Laser Crystals: Their Physics and Properties, Springer-Verlag, Berlin, New York, 1990. [27] H. Desirena, E.D.l. Rosa, A. Shulzgen, S. Shabet, N. Peyghambarian, J. Phys. D 41 (2008) 095102. [28] D.K. Sardar, D.M. Dee, K.L. Nash, R.M. Yow, J.B. Gruber, R. Debnath, J. Appl. Phys. 102 (2007) 083105. [29] A. Kaminskii, K. Ueda, A. Konstantinova, H. Yagi, T. Yanagitani, A. Butashin, V. Orekhova, J. Lu, K. Takaichi, T. Uematsu, M. Musha, A. Shirokava, Crystallogr. Rep. 48 (2003) 868. [30] W.F. Krupke, M.D. Shinn, J.E. Marion, J.A. Caird, S.E. Stokowski, J. Opt. Soc. Am. B 3 (1986) 102. [31] M.J.F. Digonnet, Society of Photo-optical Instrumentation, Selected Papers on Rare-Earth-Doped Fiber Laser Sources and Amplifiers, SPIE Optical Engineering Press, Bellingham, Washington, 1992. [32] L.M.S. El-Deen, M.S.A. Salhi, M.M. Elkholy, J. Alloys Compd. 465 (2008) 333. [33] X. Shen, Q. Nie, T. Xu, Y. Gao, Spectrochim. Acta A 61 (2005) 2189. [34] Z. Jin, Q. Nie, T. Xu, S. Dai, X. Shen, X. Zhang, Mater. Chem. Phys. 104 (2007) 62. [35] H. Lin, E.Y.B. Pun, S.Q. Man, X.R. Liu, J. Opt. Soc. Am. B 18 (2001) 602. [36] X. Feng, S. Tanabe, T. Hanada, J. Am. Ceram. Soc. 84 (2001) 165. [37] T. Xu, X. Zhang, S. Dai, Q. Nie, X. Shen, X. Zhang, Physica B 389 (2007) 242. [38] J. Yang, S. Dai, N. Dai, S. Xu, L. Wen, L. Hu, Z. Jiang, J. Opt. Soc. Am. B 20 (2003) 810. [39] S. Xu, Z. Yang, S. Dai, J. Yang, L. Hu, Z. Jiang, J. Alloys Compd. 361 (2003) 313. [40] H. Kühn, S.T. Fredrich-Thornton, C. Kränkel, R. Peters, K. Petermann, Opt. Lett. 32 (2007) 1908. [41] D.S. Sumida, T.Y. Fan, Opt. Lett. 19 (1994) 1343. [42] B. Di Bartolo, G. Armagan, International School of Molecular, Spectroscopy of Solid-State Laser-Type Materials. Plenum Press, New York, 1987. [43] D. Dexter, J. Chem. Phys. 21 (1953) 836. [44] W.Q. Shi, M. Bass, M. Birnbaum, J. Opt. Soc. Am. B 7 (1990) 1456. [45] G. Liao, Q. Chen, J. Xing, H. Gebavi, D. Milanese, M. Fokine, M. Ferraris, J. Non- Cryst. Solids 355 (2009) 447. [46] G.A. Hebbink, L. Grave, L.A. Woldering, D.N. Reinhoudt, F.C.J.M. van Veggel, J. Phys. Chem. A 107 (2003) 2483. [47] J. Massera, A. Haldeman, J. Jackson, C. Rivero-Baleine, L. Petit, K. Richardson, J. Am. Ceram. Soc 94 (2010) 130. [48] D.E. Day, J.M. Stevels, J. Non-Cryst. Solids 14 (1974) 165. [49] S.A. Payne, M.L. Elder, J.H. Campbell, G.D. Wilke, M.J. Weber, J. Am. Ceram. Soc. 28 (1991) 253. [50] G.A. Kumar, A. Martinez, E. Mejia, J.G. Eden, J. Alloys Compd. 365 (2004) 117.
Page 1 and 2: Optical characterization of Er 3 þ
Page 3 and 4: 1912 multiplet manifolds 2Sþ1 LJ t
Page 5: 1914 Table 3 Fluorescence lifetime

Optical characterization of Er3+and Yb3+ co-doped barium ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?