Polymeric slot waveguide structure, which pushes the mode field toward the surrounding media, was designed and characterized. The slot waveguide was fabricated by using nanoimprint lithography, and the operation of the slot was demonstrated at 633 nm wavelength with an integrated Young interferometer. The experimental result shows that the nanolithography method provides possibilities to fabricate disposable slot waveguide sensors.
"For instance, gratings have been used to establish the light coupling into or out from the waveguide. To enhance the light interaction with the ambient, a waveguide structure consisting of a few hundred nanometerwide slots has been demonstrated , . The nanoslot waveguide configuration has an attractive property in simultaneously guiding the light propagation and maintaining a strong light–ambient interaction. "
[Show abstract][Hide abstract] ABSTRACT: A nanoimprint mold for optical waveguide applications was fabricated by combining photolithography and focused ion beam (FIB) milling. The feasibility of the proposed method was demonstrated by imprinting 15-mm-long Y-branch waveguides, which had nanoscale slots embedded in one arm. Structural analysis of the FIB milled region showed surface roughness values below 2.5 nm. Characterization of the fabricated waveguides proved that 44% of the optical power was transmitted through the slot-embedded waveguide arm. Operation of slot waveguide was demonstrated at a wavelength of 1305 nm using Young interferometer devices.
[Show abstract][Hide abstract] ABSTRACT: The refractive index sensitivity of a polymer slot waveguide coated with a bilayer of Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> was investigated theoretically and optimized for biosensor applications. The influence of atomic-layer-deposition-coated thin high-refractive-index layers on the slot confinement factor and the homogeneous sensitivity of polymer slot waveguides with different geometries were simulated. The results were compared with those of an optimized noncoated polymer slot waveguide, both operating at visible wavelengths. The simulations reveal that the proposed structure offers a significant improvement in the confinement factor and the sensitivity. These calculations present guidelines for the design and fabrication of relatively sensitive polymer slot waveguide devices for low-cost biochemical sensor applications.
[Show abstract][Hide abstract] ABSTRACT: A refractive index sensor based on slot waveguide Young interferometer was developed in this work. The interferometer was fabricated on a polymer platform and operates at a visible wavelength of 633 nm. The phase shift of the interference pattern was measured with various concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally observed to detect a refractive index difference of 6.4 × 10<sup>-6</sup> RIU. Furthermore, the slot Young interferometer was found to compensate for temperature variations. The results of this work demonstrate that high performance sensing capability can be obtained with a polymeric slot Young interferometer, which can be fabricated by a simple molding process.
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