Optically active Er3+–Yb3+ codoped Y2O3 films produced by pulsed laser deposition

Optically active Er3+:Yb3+ codoped Y2O3 films have been produced on c-cut sapphire substrates by pulsed laser deposition from ceramic Er:Yb:Y2O3 targets having different rare-earth concentrations. Stoichiometic films with very high rare-earth concentrations (up to 5.5 × 1021 at cm− 3) have been achieved by using a low oxygen pressure (1 Pa) during deposition whereas higher pressures lead to films having excess of oxygen. The crystalline structure of such stoichiometric films was found to worsen the thicker the films are. Their luminescence at 1.53 μm and up-conversion effects have been studied by pumping the Yb3+ at 0.974 μm. The highest lifetime value (up to 4.6 ms) is achieved in films having Er concentrations of ≈ 3.5 × 1020 at cm− 3 and total rare-earth concentration ≈ 1.8 × 1021 at cm− 3. All the stoichiometric films irrespective of their rare-earth concentration or crystalline quality have shown no significant up-conversion.