Leila Ahmadi

We present a convenient, low-cost, and mass-production-compatible technique for the fabrication of strip-loaded waveguides. The technique is based on the atomic layer deposition of a slab waveguide, nanoimprinting of a strip, and integration of two structures by lamination. The guiding layer is chosen to be a 200 nm thick titanium dioxide film. The waveguide characteristics are determined by the use of ring resonators. The technique is demonstrated for titanium dioxide thin films, but it is applicable to any other material that meets the refractive index difference condition between the loading strip and the slab waveguide.

We demonstrate a polymer slot waveguide Young interferometer coated with a bilayer of Al₂O₃/TiO₂. The approach enables relaxed dimensions of the polymer waveguide which simplifies the fabrication of the structure with a resolution of 50 nm. The layers were coated by an atomic layer deposition technique. The feasibility of the device was investigated by exploiting the interferometric structure as a bulk refractive index sensor operating at 975 nm wavelength for detection of an ethanol-water solution. A refractive index change of 1 × 10⁻⁶ RIU with a sensing length of only 800 µm was detected. The approach confirms the possibility of realizing a low cost device with a small footprint and enhanced sensitivity by employing the TiO₂ rails in the sides of the slot waveguide.