Abstract: We report on a method for the simultaneous determination of refractive index profiles and mode indices from the measured near-field intensity profiles of optical waveguides. This method has been applied to UV-written single-mode optical waveguides in LiNbO<sub>3</sub> for the optimization of the writing conditions. The results for the waveguides written with light of the wavelengths 275, 300.3, 302, and 305 nm for different writing powers and scan speeds reveal that for optimum writing... Show More
Full-text available · Article · Sep 2009 · Journal of Lightwave Technology
The computed peak temperature (89 o C) for constant-room-temperature absorption coefficient is negligible for any possible lithium thermal diffusion, whereas, for temperature dependent absorption coefficient the computed peak temperature of the crystal reaches the melting point (1257 o C) which eventually supports the lithium diffusion model of UV-written waveguides at 305 nm wavelength. As the peak temperature at the surface of LiNbO 3 reaches the melting point, there will be surface damage which is evident from the microscopic observation of the optical waveguides written at 305 nm laser wavelength . A decrease in electro optic coefficient (r 33 ) has also been obtained for all UV-written waveguides , which is the result of heated portion of the waveguide above Curie temperature (1145 o C).