As the sensitivity and detection limit of photonic refractive index (RI) biosensor increases, the temperature dependence becomes a major challenge. In this paper, we present a Mach-Zehnder Interferometer (MZI) biosensor based on silicon nitride slot waveguides. The biosensor is designed for minimal temperature dependence without compromising the performance in terms of sensitivity and detection limit. With air cladding, the measured surface sensitivity and detection limit of MZI biosensor reach 7.16 nm/(ng mm(-2)) and 1.30 (pg mm(-2)), while achieving a low temperature dependence is 5.0 pm/° C. With water cladding, the measured bulk sensitivity and detection limit reach 1730(2π)/RIU and 1.29 × 10(-5) RIU respectively. By utilizing Vernier effect through cascaded MZI structures, the measured sensitivity enhancement factor is 8.38, which results in a surface detection limit of 0.155 (pg mm(-2)).
We present a label-free aptamer sensor based on an array of silicon micro-ring resonators. An array of sensors consists of three sensor rings and a reference ring was fabricated and its surface sensitivity and the limit of detection was obtained using polyelectrolyte multilayer. The mass sensitivity and the limit of detection of the fabricated sensor ring is 0.35 nm/ng mm -2 and 42.8 pg/mm 2 in air and 0.24 nm/ngmm -2 and 62.5 pg/mm 2 in water, respectively. We successfully demonstrated the binding assay over a broad range of protein concentrations using a model system with human thrombin as the analyte and DNA aptamers as immobilized ligands.
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