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LASER SYSTEMS AND MATERIALS
Radiation characteristics of crystals and nanoceramics based on
CaF2:SrF2:YbF3
M.Kh. Ashurov1, S.T. Boyboboeva12, I. Nuritdinov1, P.P. Fedorov3
1Institute of Nuclear Physics of the Academy of Sciences of the Republic of Uzbekistan, 2TRChSPI, st. Amir Temur, 104, Chirchik, 111700, Uzbekistan 111700 3FRC "GIP RAS named after by A.M. Prokhorov" st. Vavilova 3, 119991 Moscow, Russia (ashurov49@mail.ru; izzatilloh@yahoo.com; sohibaboyboboeva@gmail.com)
The interest of researchers in studying the properties of single-crystal and nanoceramic CaF2:SrF2:YbF3 compounds is due to their special position as promising laser materials pumped by laser diodes, as well as the possibility of obtaining tunable laser radiation based on them [1-3]. It was shown in [4] that such a ternary system has the so-called saddle point in which the compositions of the melt and crystal are the same, i.e. congruent melting takes place. As a result, the stability of synthesis in the concentration vicinity of this point is considerably higher, which makes it possible to obtain high-quality single crystals of solid solutions without cells at molar concentrations of Yb3+ ions equal to 3-10 %. The synthesizing process of single crystals of solid solutions CaF2:SrF2:YbF3, which provides a lower lasing threshold and higher efficiency (total efficiency is 53%, differential efficiency is 83%) of lasers, based on them, is simpler than the synthesis of single crystals of the MeF2:YbF3 (Me=Ca, Sr) [3]. In this work, comparative studies of the effect of gamma radiation in single crystals and nanoceramics of CaF2:SrF2:YbF3 solid solutions were carried out.
The optical absorption spectra of the initial crystal and ceramic samples on the basis of 65CaF2:30SrF2:5YbF3 had identical optical absorption spectra, which contained bands in the UV- region with maxima at 227, 261, 273, 300, and 361 nm, as well as a group of lines in the wavelength range of 860-1060 nm, with maxima at 922, 930, 966, 975, 1010 nm in the IR-region. Under excitation gamma irradiation at room temperature in the doses range of 105-108 rad, the intensities of all bands of Yb2+ ions in the wavelength range of 200-400 nm increase, the intensities of the line groups of Yb3+ ions in the range 860-1060 nm decrease slightly in both types of samples, which indicates a valence Yb3+^Yb2+ transition on impurity ions. The valence change of Yb3+ ions under irradiation is more pronounced in single crystals. Analysis and comparison of the optical absorption spectra of the initial, irradiated, and samples kept after irradiation at room temperature show that, in the samples under y -irradiation and holding after-irradiation, in addition to Yb3+^Yb2+ transitions, complex Yb3+^Yb3+ transformations occur within the Yb3+ - states themselves.
The surface state analysis of the single crystals and nanoceramics of solid mixtures CaF2:SrF2:YbF3, carried out using a scanning probe microscope, showed that the average height of roughness on the ceramic surface decreases from Ra=74,18 nm (initial) to Ra=55,94 nm (irradiated to 107 rad), but on the surface of the crystal it increases from Ra=5,86 nm (initial) to Ra=41,06 nm (irradiated to 107 rad). The ratio of the average height of the roughness tubercle on the surface of the irradiated and unirradiated samples shows that many defects appear in the crystal under the influence of Y-irradiation, which corresponds to a stronger Yb3+^ Yb2+ valence transition associated with the loss of interstitial fluorine. It is assumed that in nanoceramics, in contrast to single crystals, there are interfaces between "grains" and "voids" strongly developed, which impede the movement of fluorine ions and the repeated reduction of the initial Yb3+ state.
1. AkchurinM.Sh., Basiev T.T., Demidenko A.A. et al. CaF2:Yb lazer ceramics. Opt. Mater. 2013. V. 35. P. 444-450.
2. Sulc, H. Jelinkova, M. E. Doroshenko et al. Tunability of lasers based on Yb3+ doped fluorides SrF2, SrF2-CaF2, SrF2-BaF2 and YLF. Conference Paper, February 2009. 2009 OSA / ASSP 2009
3. T.T.Basiev, M.E. Doroshenko, P.P. Fedorov,. Efficient laser based on CaF2-SrF2-YbF3 nanoceramics // Optics Letters. 2008. V. 33(5). P. 521-523.
4. Stasyuk V.A. abstract. kand. dis. (M., MIXT im. M.V. Lomonosova, 1998)
