Strip-loaded waveguide on titanium dioxide thin films by nanoimprint replication

Strip-loaded Mach-Zehnder interferometer for absolute refractive index sensing

This paper presents the design, fabrication, and characterization of a Mach-Zehnder interferometer (MZI) on a strip-loaded platform specifically developed for the measurement of refractive index variations in liquids. A novel approach of large opening in the sensing region enhances the sensitivity by using the analyte as the loading strip. This allows surpassing the performances of the conventional perforations and trenched-based MZIs and prevent protecting the reference arm. The implementation of this design resulted in a high confinement factor of approximately 23[Formula: see text] in the cladding, enabling an effective interaction between the evanescent field and analyte. Ethanol-water solutions with varying concentrations were used as analyte for the characterization of the device. The strip-loaded waveguide was a 200 nm TiO[Formula: see text] thin film on a silicon dioxide wafer and a 1.2 [Formula: see text]m wide for 800 nm-thick nLOF resist served as loading strip. The sensing area featured a 10 [Formula: see text]m wide open-ing in the loading material with a sensing length of 5 mm. The homogeneous sensitivity was experimentally determined to be 0.128, demonstrating the effectiveness of the proposed design, which enabled a refractive index change monitoring of 10[Formula: see text].

Optimized ICPCVD-Based TiO2 for Photonics

We propose obtaining TiO₂ films by ICPCVD for the fabrication of low-loss waveguides. The challenge is to produce a dense and homogeneous layer with a high refractive index and low absorption in the visible range. Crystallized layers with features such as grains and amorphous layers have a rather low index for the application targeted, so we aimed for an intermediate state. We investigated the influence of plasma power, pressure, deposition time and annealing temperature on the structural, crystalline, and optical properties in order to tailor them. We showed that crystallization into rutile at the nanoscale occurred during deposition and under wisely chosen conditions, we reached a refractive index of 2.5 at 630 nm without creating interfaces or inhomogeneity in the layer depth. Annealing permits one to further increase the index, up to 2.6. TEM analysis on one sample before and after annealing confirmed the nano-polycrystallization and presence of both anatase and rutile phases and we considered that this intermediate state of crystallization was the best compromise for guided optics.

Towards accessible nanophotonics: multimode interferometer on strip-loaded slot waveguide

Nano- and micro-photonics are the key-enabling tools for future integrated components and circuitry operating at low power and high speed. By using a strip-loaded platform, we show how we can dramatically reduce the complexity, in terms of fabrication and tolerances, of the most advanced devices. Different configurations of multimode interference devices are presented. We show the design, fabrication, and optical characterization of these components.