摘要： Ytterbium-doped calcium fluoride (Yb:CaF2) is a recognized material for short-pulse power-scalable oscillators at ~1 μm [1]. It combines attractive thermo-mechanical properties of the host (thermal conductivity: 9.7 W/mK) with smooth and broad gain spectra for Yb3+ ions supporting broadband tuning of the laser emission and generation of sub-100 fs pulses in the mode-locking operation mode [1,2]. Nowadays, Yb:CaF2 crystals are widely used in high-power bulk continuous-wave (CW) and pulsed lasers and amplifiers. In the present work, we aimed to explore the potential of this material in waveguide laser geometry. Single-crystalline 1.4 at.% Yb:CaF2 thin films were grown by the Liquid Phase Epitaxy (LPE) method on bulk CaF2 substrates grown by the Czochralski method. As a solvent for the LPE growth, CaCl2 was used, Fig. 1(a). High optical quality Yb:CaF2 layers with a thickness of 27±1 μm were obtained, Fig. 1(b). The spectroscopic study indicates the predominant coordination of isolated Yb3+ ions in trigonal oxygen-assisted sites, C3v(T2), with a minor fraction of clusters contrary to bulk crystals [3], Fig. 1(c). The maximum stimulated-emission cross-section σSE is 0.70×10-20 cm2 at 974.9 nm (zero-phonon-line transition). The lifetime of Yb3+ ions is 2.10 ms. The refractive index variation due to the Yb3+ doping, ?n = nlayer – nsubstrate, was measured to be 5×10-3 at 633 nm.