Liquid Phase Epitaxy growth, structure and spectroscopy of highly-doped 20 at.% Yb3+:LiYF4 thin films

Abstract Highly doped (20 at.%) Yb3+:LiYF4 single-crystalline thin films are grown on (001)-oriented bulk undoped LiYF4 substrates by Liquid Phase Epitaxy using lithium fluoride (LiF) as a solvent. The growth temperature lies around 741 °C (0.5–1 °C supercooling) and the growth rate is 1.8–2.6 μm/min. The single-crystalline nature of the films is confirmed by X-ray diffraction and polarized Raman spectroscopy. The film morphology is studied and discussed. The polarized spectroscopic properties of Yb3+ ions are reported, indicating a stimulated-emission cross-section of 0.88 × 10−20 cm2 at 993.9 nm in π-polarization and a radiation trapping free lifetime of the 2F5/2 state of 2.00 ms indicating weak concentration-quenching. The crystal-field splitting of Yb3+ multiplets is resolved at 12 K. Highly-doped Yb3+:LiYF4/LiYF4 homoepitaxies are promising for waveguide and thin-disk lasers at ~1 μm.