Abstract

Titanium-diffused LiNbO₃ waveguide switches and modulators are foreseen as elements in optical switching networks¹⁾ or external modulators²⁾ in high bit-rate optical communication systems, because of their broadband and low loss capability. In practical applications, both low insertion loss, when coupled to optical fibers, and low operating voltage for high speed driving are required in these devices. Recently, low Ti:LiNbO₃ waveguide to single-mode fiber coupling loss has been reported.³⁾ The relation between drive voltage and waveguide structure has also been discussed.⁴⁾ However, a low loss and low drive voltage switch or modulator has not been realized, because the conditions for achieving the above two purposes are different. That is, mode size matching between waveguide and fiber is required for low loss coupling. On the other hand, small mode size is preferable for low drive voltage.

© 1984 Optical Society of America