Crystal growth and VUV luminescence properties of Er3+- and Tm3+-doped LiCaAlF6 for detectors

Er- and Tm-doped LiCaAlF6 (LiCAF) single crystals were grown by the micro-pulling-down (μ-PD) method. The crystals were transparent, 2.0 mm in diameter and 30–40 mm in length. Neither visible inclusions nor cracks were observed. Photoluminescence spectra of Er- and Tm-doped LiCAF were measured. Broad band emission due to the Tm3+ and Er3+ 5d–4f transitions dominated the spectrum at 163.5 and 165 nm respectively. These emissions had shortest wavelength among the fluoride crystal hosts ever reported at room temperature experiments. The vacuum ultraviolet (VUV) luminescent crystals are attractive as scintillators for radiation detectors, which employ photosensitive gases (such as TMAE or TEA) or photocathodes (such as CsI) sensitive mostly to VUV photons.