Growth, spectral and laser properties of Bi,Ge,O,, crystals doped with TR3+ (Dy3+, Ho3+, Tm3+, Er3+, or Yb3+) ions, are investigated. Absorption and luminescence spectra of Er3+ and Yb3+ ions are analysed and their crystal-field splitting schemes according t o energies u p t o 18400 cm-l determined. Using the Judd-Ofelt approach of electric-dipole transitions, the integral absorption coefficients of Er3+ ions are analysed. The intensity parameter Qt, transition probabilities from some excited states, and inter-manifold luminescence branching ratios are calculated. Ergebnisse uber Ziichtung, Spektroskopie und Lasereigenschaften von Bi,Ge,O,,-Einkrist~Ilen, dotiert mit den Seltenerdionen Dy3+, Ho3+, Tm3+, Er3+ bzw. Yb3+, werden mitgeteilt, weiterhin fur Er3+ und Yb3 + die Absorptions-und Lumineszenzspektren sowie die Aufspaltungsschemata im Kristallfeld. Die integralen Absorptionskoeffizienten von Er3+-Ionen werden anhand der Judd-Ofelt-Naherung fur elektrische Dipoliibergange snalysiert und der Intensitatsparameter Q t , die Ubergangswahrscheinlichkeiten einiger angeregter Zustande und die Verzweigungsverhaltnisse in die verschiedenen Lumineszenzkanale berechnet . 2. Crystal Growth and Investigation Methods 2.1 Growth of Bi,Ge,O,,:TR3+ single crystals Single crystals of bismuth germanate were grown from the melt (melting point 1044 "C) by the Czochralski technique [cf. 1, 3 to 6, 8, 91 using platinum crucibles and rf heating. Stoichiometric amounts of Bi,O,, TR,O,, and GeO, (each of 99.99% purity) 47*

T. I. BUTAEVA (b), V. A. FEDOROV (a), and S. E. SARKISOV (a) Detailed spectral physical investigations of the (Y1-zErz)&15012 and (Lul -ZErs)&16012 garnet systems in a wide Era+ ion concentration range (z = 0.003 to 1) is carried out. The calculation of the Qt intensity parameters in terms of the induced electric dipole transition theory is completed, and the influence of the data on hypersensitive transitions, as well, as the role of the TRa+ ion wavefunction choice to the results of said calculation is discussed. The estimation of the contribution, stipulated by the induced oscillating dipole moments of the ligands in the value of the B, parameter is carried out. Intermanifold luminescence branching ratios for all initial laser states of the ErS+ ions connected with the stimulated emission process are calculated. The possibility of using the concept of "spectroscopic quality" of an activated medium in the case when the intensity parameter P, =)= 0 is discussed. The precise measurements of 3 pm stimulated emission spectral composition a t e 110 and 300 K are carried out. The energy of the Stark levels of the 4111/2 and *I1312 manifolds is defined. All 3 pm induced transitions are identified and the laser kinetics at their wavelengths is studied.

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Laser action excitation conditions are found for new transitions of Er3+ ions in Lu3Al5O12 crystals at 300 K. With the use of the desactivation method, the way of laser parameter improvement is shown for Er3+ ions at the generation on the “self‐saturating” 4I11/2 → 4I13/2 transition (2.69 to 2.94 μm). The crystal field splitting schemes are given of the manifolds involved in the stimulated emission processes together with the identification of all registered laser transitions.

The main types of inhomogeinity in rhombic aluminate crystals doped with Pr3+ ions arise from light scattering particles and lattice defects causing colour center formation under short wavelength radiation. It is shown that additional electron and hole traps (iron and praseodimium ions) change the direction of processes of charge carrier release and capture as compared with the case of pure crystals.