Chapter 58 Excited state phenomena in vitreous materials

Photoluminescence properties, Judd-Ofelt analysis, and optical temperature sensing of Eu3+-doped Ca3La7(SiO4)5(PO4)O2 luminescent materials

A series of Eu³⁺-doped Ca₃La₇(SiO₄)₅(PO₄)O₂ (CLSPO) multifunctional phosphors were synthesized by a high-temperature solid-state reaction method. The crystal structure of the CLSPO host was explored using Rietveld refinement. The photoluminescence properties of CLSPO: Eu³⁺ phosphors were investigated systematically. Upon 392 nm near-ultraviolet light excitation, the phosphor exhibited strong characteristic emissions of Eu³⁺ ions with a dominant red emission peak around 613 nm, indicating its potential use in solid-state lighting. Calculations of Ω₂ and Ω₄ Judde-Ofelt intensity parameters provided insight into the structure-luminescence correlation in the CLSPO: Eu³⁺ system. By exploring the temperature sensitivity of photoluminescence intensity, the application potential of the sample to optical thermometry was studied.

2.8 μm emission and OH quenching analysis in Ho3+ doped fluorotellurite-germanate glasses sensitized by Yb3+ and Er3

The use of Yb³⁺ and Er³⁺ co-doping with Ho³⁺ to enhance and broaden the Ho³⁺: ⁵I₆ → ⁵I₇ ~2.8 μm emissions are investigated in the fluorotellurite-germanate glasses. An intense ~3 μm emission with a full width at half maximum (FWHM) of 245 nm is achieved in the Er³⁺/Ho³⁺/Yb³⁺ triply-doped fluorotellurite-germanate glass upon excitation at 980 nm. The glass not only possesses considerably low OH⁻ absorption coefficient (0.189 cm⁻¹), but also exhibits low phonon energy (704 cm⁻¹). Moreover, the measured lifetime of Ho³⁺: ⁵I₆ level is as high as 0.218 ms. In addition, the energy transfer rate to hydroxyl groups and quantum efficiency (η) of ⁵I₆ level were calculated in detail by fitting the variations of lifetimes vs. the OH⁻ concentrations. The formation ability and thermal stability of glasses have been improved by introducing GeO₂ into fluorotellurite glasses. Results reveal that Er³⁺/Ho³⁺/Yb³⁺ triply-doped fluorotellurite-germanate glass is a potential kind of laser glass for efficient 3 μm laser.

Optical properties of Lead bismuth borate glasses doped with neodymium oxide

Neodymium doped Lead bismuth borate glasses with the composition of 25PbO-25Bi2O3-50B2O3:xNd2O3, where x=0.5, 1, 1.5 and 2 mol%, have been prepared by melt quenching technique. The behavior of the density and molar volume allows concluding that, addition of Nd2O3 leads to the formation of non-bridging oxygen. Rare earth ion parameters have been calculated and studied. The optical band gap (Eg), and band tails (Ee) were determined. Judd-Ofelt theory for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω2, Ω4 and Ω6 for glass. It was observed that the deviation parameters, rms, was found to be 0.56:0.58(×10(-6)). The estimated Judd-Ofelt parameters were found to be Nd2O3concentration dependent. The hypersensitive transition, (4)I9/2→(4)G5/2+(2)G7/2, is closely related to Ω2 parameter.

Spectroscopic and laser properties of Sm³⁺ ions doped lithium fluoroborate glasses for efficient visible lasers

The Sm(3+)-doped lead barium zinc lithium fluoroborate (LBZLFB) glasses of composition 20PbO + 5BaO + 5ZnO + 10LiF + (60-x) B(2)O(3) + xSm(2)O(3), (where x=0.1, 0.5, 1.0, 1.5 and 2.0 mol%) have been prepared by conventional melt quenching technique and their structural and spectroscopic behavior were studied and reported. The amorphous nature of these glass samples was confirmed with XRD studies. The FT-IR and FT-Raman spectra reveal that, the glasses contain BO(3), BO(4), non-bridging oxygen and strong OH bonds. The bonding parameters and the oscillator strengths were determined from the absorption spectra. These parameters have been used to obtain the Judd-Ofelt intensity parameters. Using these intensity parameters various radiative and laser properties were predicted. The values of J-O intensity parameters suggested an increase in the degree of symmetry of the local ligand field at Sm(3+) sites. The decay rates for the (4)G(5/2) level of Sm(3+) ions have been measured and are found to be single exponential at lower concentrations (<1.0 mol%) and turn into non-exponential at higher concentrations (≥1.0 mol%), due to energy transfer through cross-relaxation. From the emission characteristic parameters of (4)G(5/2) level, it is concluded that the LBZLFB glasses could be useful for photonic devices like visible lasers, fluorescent display devices and optical amplifiers, operated in the visible region.