Emission spectroscopy is used to determine the spatial and temporal evolution of the electronic temperature (Te) and density (Ne) of the plasma generated by laser ablation in vacuum of a LiNbO3 target. It is found that whereas Ne (in the range of 1016 cm−3) decreases by a factor of 2 as the distance to the target surface increases 10 mm, Te (in the range 0.7–0.8 eV) only decreases 10% between 2 and 4 mm from the target to remain nearly constant for longer distances. While Te is almost constant in time at the studied distances, Ne presents a maximum at a time delay that increases when increasing the distance to the target surface. The space–time constancy of Te is related to a collisional decoupling of the heavy species in the plasma for distances longer than 2–4 mm.

Erbium doped Al 2 O 3 films with concentrations up to 6ϫ10 20 Er cm Ϫ3 have been prepared in a single step process by pulsed-laser deposition. Alternate ablation of Al 2 O 3 and Er targets has been used to control the in-depth distribution and in-plane concentration of Er 3ϩ ions independently. The characteristic Er 3ϩ photoluminescence response at 1.53 m has been studied as a function of the Er 3ϩ distribution. It is found that lifetime values can be greatly increased by increasing the Er 3ϩ-Er 3ϩ in-depth separation above 3 nm. This result can be related to a reduced Er 3ϩ-Er 3ϩ energy migration process. The in-plane Er 3ϩ concentration was increased by either increasing the number of pulses on the Er target or the laser energy density for ablation. By the latter method in-plane concentrations as high as 1.1ϫ10 14 Er cm Ϫ2 per layer ͑corresponding to 2 ϫ10 20 Er cm Ϫ3 ͒ were achieved, while keeping lifetime values as high as 6 ms. This result is explained in terms of shallow Er 3ϩ implantation during deposition.

Erbium-doped Al 2 O 3 films have been deposited in a single step process by pulsed laser deposition using independent ablation of Al 2 O 3 and Er targets. This procedure allows to control the Er 3ϩ ions in-depth distribution. The characteristic Er 3ϩ photoluminescence at 1.54 m shows lifetime values which increase from 6.0 to 7.1 ms when the Er 3ϩ-Er 3ϩ in-depth separation is increased from 3 to 9 nm. These results are discussed in terms of the ion-ion interaction and clustering for separations shorter than 6 nm.

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