Ultra-smooth ridge waveguides in lithium niobate fabricated by diamond blade dicing and high temperature in-diffusion of titanium

Integrated optics using lithium niobate (LiNbO3) as a substrate material has reached a mature technology level during the past decades, allowing fabricating many linear and nonlinear devices. As in many cases high intensities are required especially for nonlinear interactions, ridge waveguides in LiNbO3 substrates have the potential to allow for enhanced nonlinear, acousto-optical or electro-optical interactions when compared with channel or planar Ti in-diffused or (annealed) proton-exchanged waveguides. Recently optical grade dicing was introduced as a new approach to fabricate these structures. In [1] a circular precision saw was used to cut ridges into a planar waveguide. The planar waveguide is needed to provide the lateral confinement. Propagation losses as low as 0.5 dB cm-1 were achieved. These losses have been assumed to be due to scattering induced by the surface roughness of the diced sidewalls. In principle annealing of lithium niobate samples at temperatures above 1100 °C has proven to result in ultra-smooth surfaces [2]. However, although this would reduce surface roughness, in this way the planar waveguide would be destroyed, too. © 2013 IEEE.

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Ultra-smooth ridge waveguides in lithium niobate fabricated by diamond blade dicing and high temperature in-diffusion of titanium