Preparation and characterizations of Pr3+:CaF2 transparent ceramics with different doping concentrations

Abstract 0.2–5.0 at% Pr3+-doped CaF2 transparent ceramics were fabricated by hot-pressed processing for the first time. The phase compositions, microstructure and optical characteristics of the presented transparent ceramics were examined systematically. The average in-line transmittance of Pr:CaF2 transparent ceramics (2.0 mm thick) with high Pr3+ doping concentrations (1.0–5.0 at%) exceeds 86% at the wavelength of 1200 nm. The absorption spectrum manifests that the prepared Pr:CaF2 transparent ceramics contain some absorption peaks overlapped with emission bands of the commercial InGaN laser diodes. Further, a detailed investigation on the visible emission properties as a function of Pr3+ concentrations in CaF2 transparent ceramics was reported. The emission spectra presented two main characteristic peaks at 496 nm (bluish green) and 656 nm (red) corresponded to the transitions of 3P0→3H4 and 3P0→3F2 for Pr3+ activator ions. With the increase of the Pr3+ doping concentrations, the emission intensity and decay lifetimes decreased generally attributed to the concentration quenching effect. Details on energy transfer mechanism of Pr3+ in CaF2 transparent ceramics were demonstrated and discussed.