Thermally Stabilized 1 X 4 Ti:LiNbO3 Waveguide Switch

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).