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Bi 2 TeO 5 :Ho single crystals were grown by the Czochralski technique. Optical absorption spectra of Ho 3+ have been monitored in the 4500–25,000 cm −1 spectral and 9–300 K temperature range by high resolution Fourier Transform Spectroscopy. Luminescence excitation and emission spectra were measured at room temperature in the visible range. The intra-configurational f–f transitions of Ho 3+ were identified. The experimental absorption data were analyzed by a single-ion model, and the crystal field parameters for a C 2 -symmetry site were determined. On the basis of these calculations and analogy with the case of Er-doped Bi 2 TeO 5 , it can be inferred that Ho–Bi substitution mostly takes place at the Bi(1) sites. The Judd–Ofelt analysis was performed by fitting the polarized absorption spectra. The calculated Judd–Ofelt parameters were used to evaluate the Ho 3+ radiative transition probabilities and the branching ratios. The results are discussed in view of potential applications of Bi 2 TeO 5 :Ho 3+ as a laser material.

Macrocyclic molecules play key roles in basic processes in living organisms. Free bases and the metal complexes of porphyrins exhibit a wide range of important optical properties. In these systems the position of the most intense absorption band depends on the peripheral substituents of the macrocycle. Sol-gel methods have generally allowed the successful trapping of porphyrins into inorganic networks. The materials obtained are strong and transparent monolithic gels, but in the majority of cases the red fluorescence of the porphyrins disappears with ageing. We have evaluated the effect of the type and spatial disposition of the substituents in the porphyrin macrocycle periphery on key optical properties, with particular emphasis on the conservation of red fluorescence when porphyrins are simply trapped or covalently bonded to the inorganic matrix. Here, we report the use of the sol-gel procedures to obtain monolithic gels with the hydroxyl- or amino-substituted α, β, γ, δ-tetraphenylporphyrins, (H2T(S)PP), simply trapped or covalently bonded to the SiO2 matrix.

Samples of Eu3+ -activated PMMA:PAAc copolymers were prepared in order to investigate their spectroscopic properties. The densities, refractive indices, UV-Visible absorption and emission spectra and fluorescence decay times were obtained experimentally. These data were used in conjunction with Judd-Ofelt theory to calculate the spontaneous emission probabilities and branching ratios, as a function of the europium content. The range of the concentration was 0.1 to 2.5 % mol. Our results are combined with previous information on the optical properties of rare-earth activated polymers in order to get a better understanding of the role played by the Eu3+ ions on the polymerization process in our samples.

The Judd-Ofelt intensity parameters for f-f transitions of Er3+ ions in PMMA:PAAc copolymer samples were determined from optical absorption measurements and their dependence on the erbium content investigated within the range of 0.1 to 3.0 % mol. The densities, refractive indices and emission spectra have been measured. For our Er-PMMA:PAAc samples an effective radiative transfer between the copolymer host and the erbium ions is observed and discussed.