Ultrawide-detection-range refractive index sensor based on a two-dimensional mirror-image photonic crystal microcavity

In this work, a refractive index sensor is theoretically proposed based on a two-dimensional mirror-image SiO 2 /Si photonic crystal microcavity. The introduction of mirror-image microcavity effectively enhances the light localization and the coupling between light and liquid analyte. Results show that the sensor exhibits a high near-linear sensitivity of 493.5 nm RIU −1 with a narrow full-width at half-maximum of ∼20 nm in a broad refractive index range of 1.0 ∼ 1.5. Moreover, the detection resolution for the minimum variation of RI reaches to a level of 0.0002 RIU. For the analyses on the sensor performance (such as sensitivity, full-width at half-maximum), the dependences of all structure parameters are discussed in terms of the cylinder diameter, lattice constant, and microcavity size. This design is expected to detect the refractive index of wide-range liquid analytes in the fields of biology, chemistry, and medicine.