High optical quality LiREF(4) (RE = Tb(3+), Dy(3+), Ho(3+), Er(3+) and Yb(3+)), PrF(3) and CeF(3) single crystals have been grown by the Czochralski technique. Their magneto-optical properties have been measured and analyzed in detail in the ultraviolet-visible wavelength region, and their figures of merit as Faraday rotators have been determined. CeF(3) presents superior properties above 300 nm, showing a figure of merit higher than that of the reference material, terbium-gallium-garnet, which is nowadays used in the visible-near infrared. PrF(3) is the best rotator for the 220-300 nm range. Towards shorter wavelength and in the vacuum ultraviolet, it is shown that the LiREF(4) crystals are unique rotators. Overall, the rare-earth fluoride single crystals studied here exhibit better properties than other materials considered so far, and therefore they have potential to cover the increasing demand for new and improved Faraday rotators in the ultraviolet-visible wavelength region.

CeF3 and PrF3 single crystals are investigated as Faraday rotators for the UV-visible region. Their properties are compared with those of the industrial standard reference terbium-gallium-garnet (TGG) single crystal. In contrast to TGG, CeF3 exhibits a higher transparency in the whole near UV-visible-IR, and a remarkable higher figure of merit which rapidly increases towards the cutoff. In the case of PrF3, the transparency extends to even shorter wavelengths, and analogously to CeF3 its figure of merit increases notably in the UV. These results indicate the potential of CeF3 and PrF3 as optical isolators in the UV-visible, where at present there are no alternative candidates.

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Terbium is the key element for highly efficient green phosphors and visible-near IR Faraday isolators. We have recently shown the potential of LiTbF4 and Tb0.81Ca0.19F2.81 as visible Faraday rotators. In this work, we present a detail spectroscopic analysis of Tb3+ (4f8) in these two compounds with different crystal structures. By means of the Judd-Ofelt theory, the emission branching ratios and lifetimes of the Tb3+ excited states have been estimated. These results are compared with experimental values obtained for the emitting 5D4 level, as well as with the absolute light yield measurements. Tb3+ in LiTbF4 exhibits a high quantum efficiency, and its radiative lifetime is confirmed to be 7 ms. Instead, the ionic conductor Tb0.81Ca0.19F2.81, which presents a high concentration of vacant sites, shows a lower quantum efficiency and a radiative lifetime about three times larger than estimated. Absorption and emission spectra of Tb0.81Ca0.19F2.81 are broad, so that any fine structure of energy levels can be resolved. In contrast, a detailed study of the splitting of Tb3+ multiplets in Stark energy levels is carried out for LiTbF4.