Abstract

Z-cut LiNbO₃ waveguide devices are essential in high-speed optical fiber communication and photonic switching systems. To put them to practical use, they must be useable in wide temperature range. However, these devices usually have a large temperature dependency due to the thermally-induced pyroelectric charge on the z-cut surface. Electrodes on the highly-resistive SiO₂ buffer layer makes charge distribution ununiform and results in an undesirable electric field on waveguides as we reported previously⁽¹⁾. Drive point voltage shifts with temperature and it degrades crosstalk. Another problem is the connection between fibers and waveguides. The conventional method using Si V-groove array provides thermally stable connection⁽²⁾, but, there is often a large excess loss because of the imperfect matching between the waveguide and silicon end faces. The purpose of our research is to overcome these problems and make a thermally stable z-cut Ti:LiNbO₃ high-speed switch with low loss. To solve the first problem, we formed a Si layer with appropriate resistivity between the SiO₂ buffer layer and the electrodes to keep the surface-charge distribution uniform⁽¹⁾. We also devised a new method for attaching fibers to waveguides to make stable joints with low loss. We fabricated a low-loss, thermally stable 1X4 optical switch on z-cut LiNbO₃ and tested it in a 512-Mbps optical time division switching system⁽³⁾.

© 1989 Optical Society of America