Luminescence applications
NIR Luminescence
Er3+/Yb3+ - activated silica–hafnia planar waveguides for photonics fabricated by rf-sputtering
Figure 1: Normalized room temperature photoluminescence spectra of: (a) the 2F5/2→2F7/2 transition of Yb3+ ion, (b) the 4I13/2→4I15/2 transition of Er3+ ion for the SiO2-HfO2:Er3+-Yb3+ planar waveguide, obtained by exciting the TE0 mode at 514.5 nm
Figure 2: Photoluminescence excitation spectrum of the SiO2-HfO2:Er3+-Yb3+ waveguide and SiO2-HfO2:Er3+ waveguide. The detection wavelength was set to 1533 nm
The spectrum of Figure 1 shows the emission band located at 1500 nm due to the emission of erbium ions, and the emission band with a peak at 978 nm and a smaller peak at 1010 nm, typical of the ytterbium ion emissions in glasses. This pattern is an indication of the presence of the back energy transfer from Er3+ to Yb3+ ions. In fact, using the 514.5 nm laser line we excite directly only the Er3+ ions but an emission relative to the 2F5/2→2F7/2 transition of Yb3+ is observed. Nevertheless, the PL excitation spectra reported in figure 2 indicates that an effective energy transfer from Ytterbium to Erbium ions is present. In fact, as reported in Figure 2, the spectral shape of the excitation spectrum corresponds of the sample co-activated with Ytterbium ions to the typical Ytterbium absorption.
A. Chiasera, C. Armellini, S.N.B. Bhaktha, A. Chiappini, Y. Jestin, M. Ferrari, E. Moser, A. Coppa, V. Foglietti, P.T. Huy, K. Tran Ngoc, G. Nunzi Conti, S. Pelli, G.C. Righini, G. Speranza, "Er3+/Yb3+-activated silica-hafnia planar waveguides for photonics fabricated by rf-sputtering", Journal of Non-Crystalline Solids 355 (2009), pp. 1176–1179.Visible luminescence
Infrared-to-visible CW frequency upconversion in erbium activated silica–hafnia waveguides prepared by sol–gel route
Figure 3: Upconversion emission spectra after CW excitation at 980 nm, in the 70SiO2-30HfO2 planar waveguides doped with 0.5 mol% Er3+ as a function of the power: (a) 400 mW, (b) 340 mW, (c) 260 mW, (d) 175 mW, (e) 140 mW and (f) 85 mW
Figure 4: Upconversion intensity at 18300 cm-1 (full squares), 15150 cm-1 (open squares), and 24500 cm-1 (full triangle) as a function of the excitation power in the 70SiO2-30HfO2 planar waveguides doped with 0.5 mol% Er3+. The excitation wavelength was 980 nm. The solid lines are the result of a power law fit, which gives the indicated slopes
The value of the slope n, obtained by fitting the measured upconversion intensity as a function of the excitation power, indicates that two photons are involved in the infrared-to-green and three photons are involved in the infrared-to-blue upconversion processes.
Energy level diagram and the proposed mechanism for the red emission observed in Er3+-activated 70SiO2-30HfO2 waveguides, upon excitation at 980 nm. The upward solid arrows represent excitation by GSA, ESA or ETU mechanisms. The downward solid arrows indicate the red upconverted emission, and the dashed arrows represent cross-relaxation (CR) between the A and B ions.
R.R. Gonçalves, G. Carturan, L. Zampedri, M. Ferrari, A. Chiasera, M. Montagna, G.C. Righini, S. Pelli, S.J.L. Ribeiro, Y. Messaddeq, “Infrared-to-visible CW frequency upconversion in erbium activated silica–hafnia waveguides prepared by sol–gel route”, J. Non-Crystalline Solids 322 (2003), 306.Down-converter based on rare earth doped fluoride glass to improve Si-based solar cell efficiency
Figure 5: Room temperature photoluminescence spectra of the 2F5/2→2F7/2 transition of Yb3+ ions after excitation at 476 nm for the ZLAG glasses doped with 0,5% Pr3+ and with Ytterbium: (a) 1 mol % of Yb; (b) 2 mol % of Yb; (c) 3 mol % of Yb; (d) 5 mol % of Yb. Each spectrum was normalized to the maximum of the luminescence intensity
Figure 6: Room temperature emission spectra of Pr3+ ions for after excitation at 440 nm for the ZLAG glasses doped with 0,5% Pr3+ and: (a) 0 mol % of Yb; (b) 1 mol % of Yb; (c) 2 mol % of Yb; (d) 3 mol % of Yb; (e) 5 mol % of Yb and (f) 10 mol % of Yb. Each spectrum was normalized to the maximum of the luminescence intensity
Figure 7: Decay curves of the luminescence from the 3P0 metastable state of Pr3+ ions at 478 nm under excitation at 440 nm in function of the Yb3+ concentration.
Efficient down-conversion bulks Pr3+-Yb3+ co-doped ZLAG glasses have been developed. Emission of the ytterbium at 980 nm was observed after excitation of the praseodymium at 476 nm. We evaluated the energy transfer efficiency for the 3P0 state of the praseodymium to the ytterbium ions for the first step of the quantum cutting process. We observed an increase of the energy transfer efficiency with the concentration of ytterbium ions. The sample with 0.5 mol% of praseodymium and 10 mol% of ytterbium presents an energy transfer efficiency of 92%, similar to the best results obtained in fluoride crystals with the same doping.
G. Alombert Goget, D. Ristic, A. Chiasera, S. Varas, M. Ferrari, G. C. Righini, B. Dieudonné, B. Boulard, "Down-converter based on rare earth doped fluoride glass to improve Si-based solar cell efficiency", Proc. SPIE 8069, Integrated Photonics: Materials, Devices, and Applications, 80690N (May 31, 2011), doi:10.1117/12.886789.B. Dieudonné, B. Boulard, G. Alombert-Goget, A. Chiasera, Y. Gao, S. Kodjikian, M. Ferrari, "Up- and down-conversion in Yb3+-Pr3+ co-doped fluoride glasses and glass ceramics", Journal of Non-Crystalline Solids 377 (2013) pp. 105-109.G. Alombert-Goget, D. Ristic, A. Chiasera, S. Varas, M. Ferrari, G. C. Righini, B. Dieudonne, B. Boulard, "Rare-earth doped materials enhance silicon solar cell efficiency", 22 June 2011, SPIE Newsroom, doi: 10.1117/2.1201105.003701.Silica-Hafnia coated spherical microresonators
70SiO2-30HfO2:Er3+ coated microsphere by dip-coating technique with sol-gel route
Whispering gallery modes emission spectra of a silica microsphere of 250 µm in diameter and coated by a film of 70SiO2-30HfO2 activated with 1 mol% Er3+. The thickness of the coating is 0.8 µm. Spectra are obtained at different current of the 1480 nm pump laser