Search

Thin Er3+, Yb3+ co-doped Y2O3 films have been grown on (001) SiO2 substrates by pulsed laser deposition from ceramic targets. The influence of the active ion concentration and processing parameters on the structure, cathodoluminescent (CL) spectra and optical properties of the films have been investigated. The films were prepared in an oxygen atmosphere at pressures of 0.01 and 0.1 mbar and at 500°C substrate temperature. Blue, green and red light emissions centred at 408 nm, 562 nm and 660 nm, respectively, and an infrared (IR) spectrum centred at 1.54 µm were measured. The intensities of the CL peaks strongly depend on the Er and Yb ion concentration in the films and their ratio. An increase in Yb content at a fixed Er concentration leads to a decrease in the CL intensity in the visible range. It is higher for the films deposited at 0.1 mbar, which correlates with the better crystallinity obtained. Despite their better crystallinity, the films prepared at 0.01 mbar have a slightly higher optical transmission in the visible and near-IR range, which corresponds to the smoother surface and lower absorption measured.

Ablation of Fe by ultrashort laser pulses with durations 0.1, 1, and 5 ps were investigated experimentally. The laser fluence varied from the ablation threshold up to 100 J cm−2. Above 1 J cm−2, the ablation rate depended on the laser pulse duration, with the shortest pulse producing the highest value. A change in the ablation rate as the laser fluence increased was also observed. These results were analysed using molecular dynamics simulations. We show that the change in the ablation rate is connected to an overheating of the material above the critical point, which results in a steep rise of the pressure developed. Furthermore, due to the electron heat diffusion, the overheated volume increases and involves material located deeper than the skin depth. An increase in the pulse duration results in a decrease in the degree of overheating.