Ba2ErCl7 - a New Upconversion Material Emitting in the Near UV Region

Abstract

Most of the upconversion lasers implemented so far are based on rare earth doped oxide or fluoride crystals as well as fluoride glass fibers [1]. However, lower phonon energies of chloride and bromide materials, leading to less efficient multiphonon relaxation, are supposed to bring laser action within easier reach. Indeed, materials such as cs3er2cl9 [2] exhibit enhanced upconversion efficiencies. Unfortunately, such compounds are (in some cases extremely) sensitive to moisture. New materials that would combine efficient upconversion and stability to withstand storage, processing and operation under moderately dry conditions are subject to be found. In addition to other promising host lattices, we developed Ba2ErCl7 [3], recently reported by Japanese industrial researchers [4]. This compound shows bright greenish and white luminescence upon excitation around 800 nm and 980 nm, respectively. On the other hand, sensitivity to moisture turned out to be less critical than observed for e.g. Cs3Er2Cl9.