The photodarkening phenomenon in alumino-silicate glass preforms, doped with different ytterbium concentrations, was studied. The UV band, comprised between 180 and 350 nm, was examined before and after irradiation at 976 nm. The non-linear dependence of 240 nm band with concentration after infra-red irradiation was demonstrated and ascribed predominantly to Yb 3+ pair’s interaction. The emission spectrum after the excitation in UV spectral region showed increased intensity after photodarkening, probably due to Yb 2+ ions creation. Phenomenological photodarkening model and the possible existence of several defect types are presented.
References
[1]
Richardson, D.J.; Nilsson, J.; Clarkson, W.A. High power fiber lasers: Current status and future perspective. J. Opt. Soc. Am. B 2010, 27, B63–B92, doi:10.1364/JOSAB.27.000B63.
Koponen, J.; S？derlund, M.; Hoffman, H.J.; Kliner, D.A.V.; Koplow, J.P.; Hotoleanu, M. Photodarkening rate in Yb-doped silica fibers. Appl. Opt. 2008, 47, 1247–1256, doi:10.1364/AO.47.001247.
[4]
Likhachev, M.; Aleshkina, S.; Shubin, A.; Bubnov, M.; Dianov, E.; Lipatov, D.; Guryanov, A. Large-Mode-Area Highly Yb-doped Photodarkening-Free Al2O3-P2O5-SiO2-Based Fiber. In Proceedings of the European Conference on Lasers and Electro-Optics (CLEO Europe), Munich, Germany, 22–26 May 2011.
Engholm, M.; Norin, L.; Aberg, D. Strong UV absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV excitation. Opt. Lett. 2007, 32, 3352–3354.
[7]
Taccheo, S.; Gebavi, H.; Monteville, A.; Le Goffic, O.; Landais, D.; Mechin, D.; Tregoat, D.; Cadier, B.; Robin, T.; Milanese, D.; et al. Concentration dependence and self-similarity of photodarkening losses induced in Yb-doped fibers by comparable excitation. Opt. Express 2011, 19, 19340–19345.
[8]
Engholm, M.; Norin, L. Comment on “Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation”. Opt. Lett. 2008, 33, 1216.
[9]
Engholm, M.; Norin, L. Preventing photodarkening in ytterbium-doped high power fiber lasers; correlation to the UV-transparency of the core glass. Opt. Express 2008, 16, 1260–1268, doi:10.1364/OE.16.001260.
Yoo, S.; Basu, C.; Boyland, A.J.; Sones, C.; Nilsson, J.; Sahu, J.K.; Payne, D. Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation. Opt. Lett. 2007, 32, 1626–1628, doi:10.1364/OL.32.001626.
[12]
Carlson, C.G.; Keister, K.E.; Dragic, P.D.; Croteau, A.; Eden, J.G. Photoexcitation of Yb-doped aluminosilicate fibers at 250 nm: Evidence for excitation transfer from oxygen deficiency centers to Yb3+. J. Opt. Soc. Am. B 2010, 27, 2087–2094.
[13]
Liu, Y.S.; Galvin, T.C.; Hawkins, T.; Ballato, J.; Dong, L.; Foy, P.R.; Dragic, P.D.; Eden, J.G. Linkage of oxygen deficiency defects and rare earth concentrations in silica glass optical fiber probed by ultraviolet absorption and laser excitation spectroscopy. Opt. Express 2012, 20, 14494–14507, doi:10.1364/OE.20.014494.
[14]
Gebavi, H.; Taccheo, S.; Tregoat, D.; Monteville, A.; Robin, T. Photobleaching of photodarkening in ytterbium doped aluminosilicate fibers with 633 nm irradiation. Opt. Mater. Express 2012, 2, 1286–1291.
[15]
Auzel, F.; Pellk, F. Concentration and excitation effects in multiphonon non-radiative transitions of rare-earth ions. J. Lumin. 1996, 69, 249–255, doi:10.1016/S0022-2313(96)00104-4.
[16]
Gebavi, H.; Taccheo, S.; Milanese, D.; Monteville, A.; Le Goffic, O.; Landais, D.; Mechin, D.; Tregoat, D.; Cadier, B.; Robin, T. Temporal evolution and correlation between cooperative luminescence and photodarkening in ytterbium doped silica fibers. Opt. Express 2011, 19, 25077–25083, doi:10.1364/OE.19.025077.
[17]
Henke, M.; Persson, J.; Kuck, S. Preparation and spectroscopy of Yb2+-doped Y3Al5O12, YAlO3, and LiBaF3. J. Lumin. 2000, 87–89, 1049–1051, doi:10.1016/S0022-2313(99)00535-9.
[18]
Rydberg, S.; Engholm, M. Experimental evidence for the formation of divalent ytterbium in the photodarkening process of Yb-doped fiber lasers. Opt. Express 2013, 21, 6681–6688, doi:10.1364/OE.21.006681.
Amossov, A.V.; Rybaltovsky, A.O. Oxygen-deficient centers in silica glasses: A review of their properties and structure. J. Non-Cryst. Solids 1994, 179, 75–83.
[21]
Van Pieterson, L.; Heeroma, M.; de Heer, E.; Meijerink, A. Charge transfer luminescence of Yb3+. J. Lumin. 2000, 91, 177–193.
[22]
Krasikov, D.N.; Scherbinin, A.V.; Vasil’ev, A.N.; Kamenskikh, I.A.; Mikhailin, V.V. Model of Y2O3–Yb charge-transfer luminescence based on ab initio cluster calculations. J. Lumin. 2008, 128, 1748–1752.
[23]
Trukhin, A.N.; Golant, K.M. Absorption and luminescence in amorphous silica synthesized by low-pressure plasmachemical technology. J. Non-Cryst. Solids 2007, 353, 530–536.
[24]
Kirchhof, J.; Unger, S.; Schwuchow, A.; Jetschke, S.; Reichel, V.; Leich, M.; Scheffel, A. The Influence of Yb2+ Ions on Optical Properties and Power Stability of Ytterbium Doped Laser Fibers. In Proceedings of SPIE 2010, San Francisco, CA, USA, 23 January 2010; Volume 7598, pp. 75980B:1–75980B:11.
