Growth, structure, defects and polarized absorption spectral properties of Er:Yb:YCa4O(BO3)3 crystals

Abstract

YCa4O(BO3)3 (YCOB) crystals co-doped with 3at% Er3+ and 20at% Yb3+ were successfully grown by the Czochralski method. X-ray powder diffraction (XRPD) results show that the as-grown Er:Yb:YCOB crystal belongs to the monoclinic system with space group Cm. And the lattice parameters are a=8.076(8)Å, b=16.023(7)Å, c=3.528(4)Å and β=101.15(4)°. Crystal defects were revealed by chemical etching experiments. The density of etch pits, attributed to dislocations and observed on (010) planes, was found to be not uniform along the crystal diameter. The detailed polarized absorption spectra were measured. The polarized absorption cross sections at 977nm are 1.01×10−20, 1.22×10−20 and 1.05×10−20cm2 for E//X, E//Y and E//Z, respectively. And the polarized absorption cross sections at 1538nm is about 1.86×10−20cm2 for both E//X and E//Z, but for E//Y the result is 1.03×10−20cm2, which is much smaller. The relationship between the crystal structure and absorption spectra was discussed.