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Er3+-doped CaF2 nanoparticles (NPs) with variable dopant concentration were synthesized by a direct precipitation method. X-Ray Powder Diffraction, SEM and TEM were used to analize the crystalline structure and morphology. The spectroscopic characterization, as function of the Er3+ content, has been performed under CW and pulsed excitation. Under steady state conditions, it has been found that the intensity of the main emission bands is affected by luminescence quenching processes. The population dynamics, recorded under pulsed excitation, confirms not only the existence of quenching processes but also the occurrence of radiation trapping. The intrinsic transition probabilities of the main Er3+ emitting manifolds, in absence of quenching and radiation trapping, have been estimated through a procedure commonly used in bulk doped materials. A modified Judd-Ofelt analysis has been performed to determine the radiative transition probabilities, radiative lifetimes and branching ratios of the Er3+ levels. Finally, an estimation of the gap law in these NPs is given, This work has been partially supported by Ministerio de Ciencia e Innovación (Spain) under project COLUMNAS (PID2019–110632RB-I00)

In this paper, the luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb03: ZnO: Cr³⁺ is determined by using a method based on simultaneous multiple-wavelength measurement of photoacoustic and luminescence signal after pulsed laser excitation. The quantum efficiency found in this lattice was (10 ±4)% . This result was compared with the value found from the study of the lifetime in terms of the temperature of the luminescent levels involved. In this last case, two non-equivalent crystal sites were found for Cr³⁺ ions, and two fluorescence quantum yields were determined. After the estimation of the concentration of each site by electron paramagnetic resonance experiments, the averaged fluorescence quantum yield value was (9 ± 2)% in agreement with the previous result., Facultad de Ciencias Exactas, Centro de Investigaciones Ópticas

Non-linear behavior with respect to exciting fluence of both photoacoustic and luminescent signals in KCI:Eu(2+) , excited by laser pulses at 355 nm, were analyzed in terms of excited state absorption (ESA). Measured ESA cross-sections for 355 and 420 nm were found to be 1×10(−17)cm2 and 2×10(−18)cm2 respectively., Centro de Investigaciones Ópticas

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 22-10-2010