Laser patterning and morphology of two-dimensional planar ferroelastic rare-earth molybdate crystals on the glass surface

The laser-induced crystallization method is applied to pattern two-dimensional planar crystals consisting of ferroelastic β′-(Sm,Gd)₂(MoO₄)₃ crystals (designated here as SGMO crystals) on the surface of Sm₂O₃–Gd₂O₃–MoO₃–B₂O₃ glass. By scanning Yb:YVO₄ fiber lasers (wavelength: 1080 nm) continuously with a small pitch (0.7 μm) between laser irradiated parts, planar SGMO crystals with periodic domain structures showing different refractive indices are patterned successfully, and a high orientation of SGMO crystals is confirmed from micro-Raman scattering spectrum and second harmonic intensity measurements. It is found that the crystal growth direction is perpendicular to the laser scanning direction. This relation, i.e., the perpendicular relation, is a different from the behavior in discrete crystal line patterning, where the crystal growth direction is consistent with the laser scanning direction. The present study proposes the possibility of the control of crystal growth direction in laser-induced crystallization in glasses.