Characterization of an optical waveguide with a composite structure

A new optical waveguide (OWG) with a composite structure was designed and fabricated for chemical and biological sensing applications. The composite OWG consists of a uniform TiO/sub 2/ film and a pair of tapered SiO/sub 2/ films coated together on the surface of a single-mode potassium ion-exchanged (PIE) planar waveguide. By use of the TiO/sub 2/ film-covered SiO/sub 2/ tapers as optical directional couplers, the TiO/sub 2/ film becomes a single-mode waveguiding layer with an enhanced evanescent field and an increased surface-scattering loss. Such a composite structure can be used to make a polarimetric OWG interferometer and to make the polarization-insensitive PIE waveguide a TM polarizer. The composite OWG was characterized theoretically and experimentally.