Luminescence and damage thresholds of cerium-doped LaF3 for ns-pulsed laser excitation at 248 nm

We have studied time-resolved luminescence spectra and laser damage thresho lds of Ce:LaF3 following excitation with 248 nm/14 ns laser pulses at room temperature for the two Ce concentrations 0.03 and 1 mol %. The relative in tensities of the 5d-4f bands emitted from Ce3+ at regular and at perturbed lattice sites were found to vary linearly with time for the higher concentr ation and quadratically for the lower one. This can be explained by radiati ve energy transfer between the two sites and generation of new perturbed si tes at a rate that only shows up for the low Ce concentration. Lifetimes of the respective emission bands were determined to be about 18 ns and 41 ns. Despite resonant absorption of the 5 eV photons, surprisingly high ablatio n thresholds - 16 J/cm(2) for 0.03% Ce, and 10 J/cm(2) for 1% Ce - were obs erved by the probe-beam deflection technique. The reason is the strong ener gy loss due to intense fluorescence and deposition of the nonradiative ener gy fraction in the bulk rather than at the surface. The depth of energy dep osition was revealed by scanning electron microscopy in the form of distinc tly different ablation morphologies for the two Ce concentrations.