Thermodynamic Study on Diffusion Growth of Ga3+-Doped LiNbO3 Single Crystal Thin Film for Photonic Application.

A thermodynamic study was performed on the growth of Ga3+-doped LiNbO3 (LN) thin film. Some Ga3+-doped LN thin films were grown on the LN surface by thermal diffusion of Ga2O3 film in the temperature range of 1000-1100 °C. After growth, the Ga3+ ion in the grown thin film was profiled, and its diffusion-growth characteristics were studied. The temperature dependences of diffusion-growth coefficient and solubility were quantified. These dependences are crucial to the design and growth of a Ga3+-doped LN thin film for various photonic applications. A comparison with the case of Ti4+ diffusion-growth, which induces an increase of LN refractive index and hence formation of an optical waveguide, shows that Ga3+ grows considerably faster than Ti4+ because of its smaller ionic radius. In addition, Ga3+-doping contribution to LN refractive index was studied by measuring and comparing the refractive indices at Ga3+-grown and Ga3+-free parts of the crystal surface. The results show that the contribution is small. [ABSTRACT FROM AUTHOR]