Synthesis and laser patterning of ferroelastic β'-RE_2(MoO_4)_3 crystals (RE: Sm, Gd, Tb, Dy) in rare-earth molybdenum borate glasses

摘要

The glasses with the compositions of 22.5RE_2O_3-47.5MoO_3-30B_2O_3 (RE: Sm, Gd, Tb, and Dy) (mol%) were prepared by a conventional melt quenching method, and the formation and laser patterning of ferroelastic β'-RE_2(MoO_4)_3 crystals were examined. The initial crystalline phase was β'-RE_2(MoO_4)_3 in all the glasses, and the second crystalline phases were rare-earth borates such as Gd(BO_2)_3, Tb(BO_2)_3, and DyBO_3, and α-RE_2(MoO_4)_3 in the glass with Sm_2O_3. It was confirmed from polarized optical microscope observations and micro-Raman scattering spectra that β'-RE_2(MoO_4)_3 crystal lines having periodic refractive index changes were patterned by irradiations of continuous wave Yb:YVO_4 fiber laser (wavelength: 1080 nm, power: 0.5-2.0 W, scanning speed: 8-20 μm s~(-1)). It was found that the periodic degree of refractive index changes depends on the kind of RE~(3+) ions. The present study demonstrates that the appearance of periodic domain structures is an intrinsic feature in the laser patterning of ferroelastic β'-RE_2(MoO_4)_3 crystals.