Characterization and application of a channel–planar composite waveguide

A new structural waveguide, which is referred to as a channel–planar composite optical waveguide (COWG), has been fabricated by sputtering of a titanium dioxide $\left({\mathrm{TiO}}_2\right)$ film onto a glass substrate with potassium ion-exchanged channel waveguides. By use of a mask during deposition, the ${\mathrm{TiO}}_2$ film was formed into a 27-nm-thick, 5-mm-wide strip with two 1-mm-long tapered ends perpendicular to the channel waveguides. Adiabatic transition of the ${\mathrm{TE}}_{00}$ mode and the ${\mathrm{TE}}_{00}–{\mathrm{TM}}_{00}$ mode separation inside such a channel–planar COWG were demonstrated by combination of theoretical analysis and measurement of the experimental attenuation that arises from scattering loss and evanescent-field dye absorption. Changing the superstrate index in the region of the ${\mathrm{TiO}}_2$ film in the channel–planar COWG yielded polarimetric interference patterns. This new technique can be applied to integrated optical chemical and biological sensors to produce enhanced sensitivity.