PLD-grown Yb-doped Sesquioxide Films on Sapphire and Quartz Substrates

This paper focuses on the fabrication and characterization of crystalline Yb-doped sesquioxide films (Yb₂O₃, Yb:Lu₂O₃, Yb:Sc₂O₃) grown by pulsed laser deposition on single crystal sapphire (α-Al₂O₃) and quartz (α-SiO₂) substrates as well as on lutetia (Lu₂O₃) and scandia (Sc₂O₃) substrates. Such ytterbium doped active films can be promising for use in a thin-disk laser setup. X-Ray diffraction measurements show that the films grow highly textured along <111> direction. The ω-scan (rocking curve) shows deviation of the crystallite orientation ∼4° in case of Lu₂O₃ and Yb₂O₃ films and <1° for Sc₂O₃ films. Yb₂O₃ films reveal no luminescence at room temperature and the well known Yb³⁺ emission in the 975-980 nm region (zero-phonon line) can only be observed at temperatures below 20 K. A similar effect is observed in a bulk Yb₂O₃ crystal. Ytterbium emission and excitation spectra measured at room temperature for Yb(5%):Lu₂O₃ and Yb(4%):Sc₂O₃ films resemble those of the bulk crystal very closely. Luminescence decay lifetimes are also comparable to those measured in a bulk crystal. This indicates a high quantum efficiency of the Yb³⁺-emission and allows application of such films as active media for thin disk lasers.