Oxyfluoride glass-ceramics

Another effects of the interaction with the surrounding disordered matrix is the increase in the one-phonon direct relaxation of Ho3+ in oxyfluoride glass ceramics due to coupling to the higher density of low-frequency phonon modes in the glass compared with the crystal (Meltzer et al., 2002). The direct relaxation time between the two lowest 5Fs sublevels (a gap of 14.5 cm-1) of Ho3+ in nanocrystals of different sizes embedded in oxyfluoride glass ceramics was measured (see fig. 14), under excitation of the second low-... 

Figure 2. Emission fluorescence spectra obtained at different laser power intensities under excitation with Ar laser in a 1 mol% of Nd oxyfluoride glass sample. Emission spectrum of a 1 mol% of Nd " oxyfluoride glass ceramic sample (GC) obtained using a furnace under Ar laser excitation.

M, J, Dejneka, Transparent oxyfluoride glass ceramics, MRS Butt., 23, 57-62 (1998),... 

M, Mortier, A, Bensalah, G, Dantelle, G, Patriarche, D, Vivien, Rare-earth doped oxyfluoride glass-ceramics and fluoride ceramics Sintesis and optical properties. Opt. Mat., 29, 1263-1270 (2005), Patterning of non-linear optical crystals in glass by laser-induced crystallization, J. Am. Ceram. Soc. 90, 699-705 (2007),... 

OPTICAL GAIN BY UPCONVERSION IN Tm-Yb OXYFLUORIDE GLASS CERAMIC... 

Evidence of positive optical gain is observed in Tm -Yb codoped oxyfluoride glass ceramic in an upconversion pump and probe experiment. The G4 level of the Tm ions is populated by an upconversion mechanism under excitation of the Yb ions at 975 nm with high power pulsed laser and give rise to an intense emission from the G4 to the F4 levels. The G4 — T4 electronic transition is stimulated with a low signal at 650 nm as a probe. 

Under this condition, we reach the population inversion necessary between the Tm levels of the transition G4 —> F4 and we observed an increase of the emission intensity at the signal wavelength due to the stimulated emission. Transient positive optical gain around 4 cm" ( 17 dB/cm) has been measured in Tm-Yb codoped oxyfluoride glass ceramic. 

In this context we are investigating the optical amplification properties of trivalent lanthanide ions doped into the oxyfluoride glass ceramics, with the purpose of extending the knowledge and the application perspective of this material. In this paper we present the results of a series of pump and probe experiments carried out on oxyfluoride glass ceramics activated with Tm -Yb. ... 

Optical Gain by Upconversion in Tm-Yb Oxyfluoride Glass Ceramic... 

Figure 1- Emission spectrum for Tm -Yb codoped oxyfluoride glass ceramic associated to the G4 —> p4 electronic transition. The solid line gives the emission of the sample under pump excitation and the dashed line shows the emission under pump and probe excitation. The signal wavelength is indicated with an arrow...

Figure 2. Energy level Scheme of Tm -Yb codoped oxyfluoride glass ceramic. The Dashed lines show the upconversion process to populate G4 level of Tm ions by eneigy transfer from Yb ions which are produced by using OPO laser at 975 nm. Solid line shows the optical gain transition.

F. I.ahoz, J. M. Almenara, U. R. Rodriguez-Mendoza, 1. R. Martin, and V. Lavin, Dopant partitioning influence on the near-infrared emision of Tm in oxyfluoride glass ceramics, J. Appl. Phys. 99,053103 p006)... 

F. l.ahoz, S.E. Hernandez, N.E. CapuJ and D. Navarro-Urrios, Optical amplification in Ho -doped transparent oxyfluoride glass ceramics at 750 nm, Appl. Phys. Lett. 90, 201117 (2007)... 

S. Gonzalez-Perez, l.R. Martin, F. Rivera-Lopez, F. Lahoz, Temperature dependence of Nd —>Yb -energy transfer processes in co-doped Oxyfluoride glass ceramics, J. Non-Cryst..Solids, 353, 1951-1955 (2007). 

D.Q. Chen, Y.S. Wang, etc., Crystallization and fluorescence properties of Nd -doped transparent oxyfluoride glass ceramics, T. Materials Science and Engineering B, 123,1-6 (2005). 

The Ho " ion has a relatively wide absorption band in the 1150-1225-nm spectral range due to Ig —> % transition. The irradiation power density of sunlight in this spectral range is approximately 40 W/m, which is approximately twice more intense than that in the 1480-1580-nm range. Lahoz in 2008 reported the use of Ho singly doped oxyfluoride glass ceramics as promising upconverters for efficiency enhancement in c-Si solar cells [50]. Under sub-band gap excitation at 1170 nm, upconversion emissions in the visible (approximately 650 nm, Ig... 

Composition and Properties of Some Transparent Oxyfluoride Glass-Ceramics (Tick et al., 1995)... 

Figure 4-18 Fluorescence spectra of a) Er-Yb oxyfluoride glass, b) Er-Yb oxyfluoride glass-ceramic, c) aluminofluoride glass.

Dejneka M.J., "The Luminescence and Structure of Novel Transparent Oxyfluoride Glass-Ceramics,"/. Non-Cryst. Solids, 239, 149—55 (1998a). 

Dejneka M.J., "Transparent Oxyfluoride Glass-Ceramics," Mater. Res. Bull., 23 [11] 57-62 (1998b). 

In case of the fabrication ofoxide/fluoride composite materials, trifluoroacetate sols are mixed with solutions of other compositions. For example, an aUcoxide solution composed of tetramethylorthosilicate (TMOS), methanol, water, and A,iV-dimethylformainide (DMF) is mixed with trifluoroacetate sols in preparing Si02 -based oxyfluoride glass-ceramics (Fujihara, 1999). However, optimal experimental conditions for the silica system alone are not necessarily suitable for the preparation of composites. Factors are concerned such as compositions, pH values, and types of catalysts. Because TFA acts as an acid catalyst in the processing ofSiOa-based systems, overall solution compositions should be simplified by understanding a role of each constituent (Fujihara, 2000c). 

Figure 10-10. Schematic diagram of typical procedures for a trifluoroacetate-based sol-gel processing of oxyfluoride glass-ceramics and thin films.

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