Growth, structure and spectral properties of a novel crystal CaErAlO4 for 2.7 μm lasers

Abstract

Novel stoichiometric CaErAlO₄ crystals were successfully grown by the Czochralski method. The structure was determined to belong to the I4/mmm space group, in which the Ca²⁺ and Er³⁺ cations share the same crystallographic site, resulting in the inhomogeneous broadening of the spectra. The spectra were measured at room temperature. The absorption peak at 972 nm with a broad FWHM of 29 nm and a high coefficient up to 23.2 cm⁻¹ is very suitable for commercial InGaAs laser diodes. In the ⁴I_11/2 → ⁴I_13/2 transition, the maximum emission peak was at 2.790 μm with a broad FWHM of 125 nm, and the emission cross section was calculated to be 1.03 × 10⁻²⁰ cm², which is on the order of that of Er³⁺:YAG. The gain cross sections were also estimated. These results imply that this CaErAlO₄ crystal may be regarded as a candidate for 2.7 μm lasers.