Optical Refractive Index Sensing Based on High-Q Bound States in the Continuum in Free-Space Coupled Photonic Crystal Slabs

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Liu, Yonghao; Zhou, Weidong; Sun, Yuze
Department of Electrical Engineering, The University of Texas at Arlington
Sensor designs -- optical; Fano resonance; Label-free sensor
article description
High sensitivity (S) and high quality factor (Q) are desirable to achieve low detection limit in label-free optical sensors. In this paper, we theoretically demonstrate that single-layer and coupled bi-layer photonic crystal slabs (PCS) possess simultaneously high S and high Q near the bound states in the continuum (BIC). We theoretically achieved S > 800 nm/RIU and Q > 107 in refractive index sensing in the 1400–1600 nm telecom optical wavelength bands. We experimentally demonstrated an S of 94 nm/RIU and a Q of 1.2 x 104, with a detection limit of 6 X10 -5 refractive index unit. These sensor designs can find applications in biochemical sensing, environmental monitoring, and healthcare.