Modelling the formation of optical waveguides produced in LiNbO <inf>3</inf> by laser induced thermal diffusion of lithium ions

Analytical and numerical modelling of the fabrication of optical waveguides in lithium niobate (LiNbO3) through direct writing with a continuous wave ultraviolet (UV) laser has been performed. It is proposed that the UV illumination induces heating of the surface and subsequent thermal diffusion of lithium which alters the refractive index in accordance with the lithium concentration dependence of the Sellmeier equations.