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Enhanced sensitivity in single-mode Si3N4 stadium resonators at visible wavelengths

Chemnitz, Mario; Schmidl, Gabriele; Schwuchow, Anka; Zeisberger, Matthias; Hübner, Uwe; Weber, Karina; Schmidt, Markus A.
in: Optics Letters (2016) 5377

Marker-free and non-invasive detection of analyte traces in aqueous solution using integrated optical resonators is an emerging technique within bioanalytics. Here, we present a single-mode silicon-nitride stadium resonator operating at the red edge of the visible spectrum, showing sensitivities larger than 200 nm/RIU and transmission dips with extinction ratios up to 15 dB. We present a mathematical model that allows optimization of the resonator sensitivity using the mode properties only, revealing that optimal sensing conditions are achieved for TM-polarized modes close to modal cut-off. The short operation wavelength makes the system especially suitable for nanoparticle enhanced sensing potentially down to the single-molecule limit.

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