Formation of LiNbO₃ crystals at the surface of TeO₂ -based glass by YAG laser-induced crystallization

Lithium niobate LiNbO₃ crystals were formed at the surface of CuO (1 mol%)-doped 25Li₂O-25Nb₂O₅-50TeO₂ glass (mol%) by heat-assisted (150 ^{{ring operator}}C) continuous-wave Nd:YAG laser irradiations with a wavelength of λ=1064 nm. Nd:YAG laser energies absorbed by Cu²⁺ ions (d-d transitions) were converted to the lattice vibrations of surrounding Cu²⁺ ions (nonradiative relaxations), giving the increase in the temperature of the laser irradiated local region. The formation of LiNbO₃ crystals was confirmed from micro-Raman scattering spectra. For the line patterned by a laser scanning with a power of 0.59 W and a speed of 6 μm/s, the possibility of a c-axis orientation of LiNbO₃ crystals along the laser scanning direction was proposed. The present study demonstrates that the combination of Cu²⁺ and Nd:YAG laser with λ=1064 nm, i.e. transition metal atom heat processing, is effective in inducting LiNbO₃ crystals in TeO₂-based glasses.