Spectral-luminescent and laser properties of the (Y1-x,Ybx)2O3−Al2O3−B2O3 glasses
Introduction
Nowadays, rare-earth ions are the main activator both for solid-state laser media and for most of other optical materials. However, the luminescence of these ions, except Gd3+, is prone to concentration quenching, which substantially limits the value of specific output of radiant energy. And if for the cerium ions such quenching occurs mainly on the formation of the Се4+–О–Се3+ clusters [1], for other ions, cross-relaxation and cooperative interactions are the main quenching factor [2]. The effectiveness of such interactions, other things being equal, is in reverse power dependence on the distance between the donor and acceptor of excitations, in the case of multipole interaction, and decreases exponentially with the index of dimension order of their electronic shells, in the case of exchange interaction [2]. It is known [3] that with increasing Ln concentration the mean-statistical distance R(Ln–Ln) is lowered to the minimum possible value (Rmin) for the given matrix, determined by specific features of its structure, whereas on further rise of Ln concentration only the number of ions disposed at this distance is increased. Therefore, the search for matrices ensuring large Rmin is of priority value in creating high-doped laser media having large specific energy output.
Recently [4], by an example of the Sm3+ ions activated yttrium-alumina-borate glasses of composition close to the stoichiometry of huntite-like (Y1−xLnx)Al3(BO3)4 crystals it was established that they are characterized by record high, for oxide matrixes, value of Rmin(Ln–Ln) amounting to 0.67 nm. Moreover, it was shown that in passing from the huntite-like crystal to the glass the limiting quantum yield of the Sm3+ luminescence, that is limited by the intra-center exchange of excitations for vibrations of the trigonal BO3 groups, increases from 55% to 80%.
Naturally, on increasing the spectral gap (ΔЕ) between the metastable and the closest lower state of the activator (for the Sm3+ ions ΔЕ ≈ 7500 cm−1) the luminescence quantum yield will enhance. For example, the yield is enhanced practically up to 100% for Tb3+ ions (ΔЕ ≈ 14700 cm−1) in the huntite-like glass [5]. In this connection, of interest are similar glasses activated by the Yb3+ ions for which ΔЕ ≈ 10000 cm−1. Due to absence of excited-state-absorption, small Stokes losses, and availability of powerful sources of light-diode pumping at λ ≈ 975 nm, these glasses are the most preferable disordered material for the accumulation of high energy density on the metastable level, while the relatively broad band of their luminescence is suitable for the realization of sub-femtosecond mode of lasing [6]. However, the attainment of maximum efficiency of lasers using Yb-containing glasses is hindered by photo-darkening and photo-bleaching as well as cooperative luminescence. The first two effects, most probably, are due to photoreduction of Yb3+ to Yb2+ in Yb−Yb clusters [7], and the latter – to super-exchange interaction between the Yb3+ ions bonded by bridge oxygen [8]. It is logical to believe that the Yb-containing huntite-like glasses, ensuring large minimum distance between the activator ions, should be characterized by both weak photo-darkening and photo-bleaching, and by low efficiency of cooperative luminescence.
Huntite-like glasses have an additional advantage thanks to relatively high physico-chemical characteristics. Specifically, their heat conductivity by 2–3 times exceeds the heat conductivity of commercial phosphate glasses [9], [10] while the coefficient of linear thermal expansion is less by a factor of 0.5–0.7 [11].
In spite of the indicated potential advantages, we failed to find in the literature any information on the spectral-luminescent and laser properties of huntite-like glasses activated by the Yb3+ ions. It is to meet this deficiency was the aim of the present work.
Section snippets
Materials and experimental procedure
For the investigation, we synthesized glasses of the composition (mol. %) 10(YbxY1-x)2O3−30Al2O3−60B2O3 characterized by somewhat increased, for better vitrification, concentration of B2O3, as compared to that in huntite-like crystal. High purity Yb2O3, Y2O3, Al(OH)3, and H3BO3 were used as initial components. Fusion was carried out in platinum crucible in electric laboratory resistance furnace with SiC heaters in air during one hour at the temperature 1480 °C; the obtained melt was poured on a
Spectral-luminescent properties
Typical LASes of a synthesized glass at different temperatures of successive annealing Tan during 15 h are displayed in Fig. 1. It is seen that annealing at Тan ≤ 720 °C does not affect the spectra of the matrix and the 2F7/2 → 2F5/2 band of the Yb3+ ions (λmax ≈ 980 nm), whereas at Тan ≥ 760 °C considerable increase in optical density occurs at λ ≤ 900 nm. Analysis of the dependence k(1/λ) for the sample of Тan = 760 °C testifies that it obeys the Rayleigh law of light scattering. This allows
Conclusions
Fused glasses of the composition (mole %): 10(YbxY1-x)2O3−30Al2O3−60B2O3 are characterized by high thermal stability (annealing at Тan ≤ 720 °C does not affect the spectra of matrix and the 2F7/2 → 2F5/2 band of the Yb3+ ions) and high value of the threshold of laser-induced destruction of such glasses surface (27 ± 3 J/≿m2). Their nonlinear index of refraction close to 2.2 × 10−13 esu. The Yb3+ ions in these glasses form one type of optical centers having the radiation decay constant of
Acknowledgement
The authors gratefully acknowledge the financial support of this research by the Belarusian and Russian Foundation for Basic Research (grant no. F15SB-028 and grant no. 16-53-00157, respectively), and the Ministry of Education and Science of Russia (grant no. 14.Z50.31.0009).
References (32)
- et al.
Influence of preparation redox conditions and composition of Ce-containing silica gel-glass on its absorption spectrum in the visible region
J. Alloys Compd.
(2002) - et al.
Spectroscopic properties of Sm-containing yttrium-aluminoborate glasses and analogous huntite-like polycrystals
Mater. Chem. Phys.
(2012) A reliable and fast method for the solution of Fredholm integral equations of the first kind based on Tikhonon regularisation
Comput. Phys. Commun.
(1992)- et al.
Charge transfer luminescence of Yb3+
J. Lumin.
(2000) - et al.
Laser performance parameters of Yb3+ doped UV-transparent phosphate glasses
Chem. Phys. Lett.
(2014) - et al.
Spectroscopic studies on Yb3+-doped tungsten-tellurite glasses for laser applications
J. Non-Cryst. Solids
(2018) - et al.
Spectroscopy of Yb-doped tungsten-tellurite glass and assessment of its lasing properties
Opt. Mater.
(2018) - et al.
Lasing improvement of Yb: phosphate glass with GeO2 modification
J. Lumin.
(2017) - et al.
Influence of lattice modifier on the nonlinear refractive index of tellurite glass
Ceram. Int.
(2017) - et al.
Lazernye Fosfatnye Stekla
(1980)
Investigation of spatial distribution of impurities in solids by the method of kinetic luminescent spectroscopy
JETP
Oxide glass with minimum distance 0.67 nm between rare-earth activators
Glass Ceram.
High-energy diode-pumped D2O-cooled multislab Yb:YAG and Yb:QX-glass lasers
Opt. Lett.
Reversible photo-darkening and resonant photo-bleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation
Laser Phys. Lett.
Covalent mechanism of cooperative transitions in lanthanide exchange-coupled pairs. Intensity calculations for double transitions in M2L11 f1–f1 dimer
Phys. Stat. Sol. (b)
Luminescent and thermo-optical properties of Nd3+-doped yttrium aluminoborate laser glasses
J. Appl. Phys.
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Effect of potassium or yttrium introduction in Yb<sup>3+</sup>-doped germano-gallate glasses on the structural, luminescence properties and fiber processing
2022, Optical MaterialsCitation Excerpt :The longest lifetime measured is 0.975 ms for GGBK-Yb0.5 and 0.928 ms for GGBY-Yb0.5, which are comparable to that reported for the Yb3+:YAG crystal (1.1 ms for a concentration of 2.5 at. % Yb3+) [16] and lead germanates [34], gallo-germanates (0.94 ms for 1 mol% Yb3+) [15] and other kinds of oxide glasses [35], but shorter than that measured for an oxyfluoride glass based on heavy metals and silicates (1.52 ms for a concentration of 2 mol% Yb3+) [25]. Our value is in accordance with the high refractive index of germano-gallates which contributes to rise the radiative cross section and indeed lower the emission lifetime.