Abstract
We propose a double-layer Fano resonance photonic-crystal-slab-based sensor (DFRPhCS) for label-free detection of different size analytes. One of the slabs is fully etched, while the other is partially etched, with three resonant dips in the transmission spectrum, which can detect and distinguish different sizes of analytes. As for bulk detection, all three resonant dips show red shifts, with the refractive index (RI) of the environment increasing, achieving sensitivity of 800 nm/RIU and detection limit of . For the detection of micrometer-level particles, due to the large analyte size, molecules are stuck on the upper slab, thereby changing the polarity and offset of the middle dip. Moreover, for nanoparticle detections, molecules can permeate the air holes. Therefore, the solution concentration variations of nanoparticles lead to middle dip wavelength shift with polarity remaining. Accordingly, the dimension and RI of the analyte can be distinguished, thereby indirectly presuming the category of the analyte. Furthermore, DFRPhCS is promising in preliminary detections and can be improved by adjusting the angle as well as polarization of the incidence appropriately.
© 2019 Optical Society of America
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