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Ca1−XYbXF2+X crystals were grown by two different methods: simple melting under CF4 atmosphere and the laser heated pedestal growth (LHPG) method under Ar atmosphere. Spectroscopic characterization (absorption, emission, Raman spectroscopy and decay curves) was carried out to identify Stark levels of Yb3+ transitions in the different crystallographic sites of the cubic structure in Ca1−XYbXF2+X crystals. The Yb3+ concentration dependence of the experimental decay time was analysed by using concentration gradient fibre in order to understand involved concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to unexpected rare earth impurities (Er3+, Tm3+) has been observed in the visible region and interpreted by a limited diffusion process within the Yb3+ doping ion subsystem towards impurities. The main parameters useful for a theoretical approach of laser potentiality have been given as τrad = 2.05 ms, N0 = 7.47 × 1021 cm−3 (32 mol%) and Nm = 6.39 × 1021 cm−3 (26.5 mol%).

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