Laser-Induced Line Patterning of Nonlinear Optical β'-Sm_xGd_2-x(MoO₄)₃ Molybdate Crystals in Glass

Abstract

Glasses in the system of Sm₂O₃-Gd₂O₃-MoO₃-B₂O₃-BaO are prepared, and structural changes are induced by irradiations of continuous wave Nd: YAG laser with a wavelength of λ=1064 nm. The optical absorption coefficient of Sm³⁺ ions at λ=1064 nm in the glasses is found to increase linearly with increasing Sm₂O₃ contents, and it is clarified that the Sm₂O₃ content in the glasses must be at least more than 6 mol% in order to induce crystallization under laser irradiations with powers less than P=1 W. The lines patterned by laser irradiations with P=0.8 W and a scanning speed of S=2.5 μm/s consist of a mixture of paraelectric α-Sm_xGd_2-x(MoO₄)₃ and nonlinear optical β'-Sm_xGd_2-x(MoO₄)₃ crystals. The formation of only β'-Sm_xGd_2-x(MoO₄)₃ crystals is confirmed in the lines patterned at P=0.83 W. Although the addition of BaO increases largely the thermal stability against crystallization, the line patterning behavior is not affected significantly at least in the present laser irradiation conditions.