Origin of periodic domain structure in Er3+-doped β′-(Sm,Gd)2(MoO4)3 crystal lines patterned by laser irradiations in glasses

Er3+-doped β′-(Sm,Gd)2(MoO4)3 crystal lines are patterned on the surface of Er2O3–Gd2O3–Sm2O3–MoO3–B2O3 glasses by continuous-wave Yb:YVO4 laser irradiations (wavelength: 1080 nm, power: 1.3 W, scanning speeds: 5 μm/s), and the origin of the periodicity of self-organized domain structures with high and low refractive index regions in crystal lines is examined from polarized optical microscope (POM) observations, micro-Raman scattering spectrum, and photoluminescence spectrum measurements. It is found that the periodicity of domain structures changes largely depending on Er2O3 content, i.e., the length of high (bright color in POM observations) and low (dark color) refractive index regions increases with increasing Er2O3 content and homogeneous crystal lines with no periodic domain structures are patterned in Er2O3–Sm2O3–MoO3–B2O3 glass with no Gd2O3. Considering that the degree of ferroelasticities in β′-(Sm,Gd)2(MoO4)3 crystals decreases due to the incorporation of Er3+ ions, it is demonstrated that the origin of periodic domain structures in laser-patterned lines is due to spontaneous strains in ferroelastic β′-(Sm,Gd)2(MoO4)3 crystals.

Graphical abstractThis figure shows the polarized optical photographs (top view) for the lines patterned by laser irradiations with the power of P=1.3 W and the scanning speed of S=5 μm/s in xEr2O3–(18.25−x)Gd2O3–3Sm2O3–63.75MoO3–15B2O3 (mol%) glasses. This figure indicates that the periodicity of domain structures in β′-(Sm,Gd)2(MoO4)3 crystal lines, i.e., the lengths of bright (high refractive index) and dark (low refractive index) color regions, changes depending on the amount of Er2O3 addition. It is demonstrated that the origin of the periodicity of domain structures is due to spontaneous strains in ferroelastic β′-(Sm,Gd)2(MoO4)3 crystals.Figure optionsDownload full-size imageDownload as PowerPoint slide