Dynamic colorimetric sensing with all-dielectric metasurfaces governed by bound states in the continuum†

Abstract

High-sensitivity refractive index (RI) colorimetric sensing is achieved by utilizing the all-dielectric bound in continuum (BIC) metasurface in this work. By adjusting the spacing between the nanodisk dimers of the lithium niobate (LN) metasurface, the transformation of BIC into QBIC has resulted in a reflection resonance with a bandwidth of less than 1 nm and a reflection efficiency of up to 98%. This resonance peak is suitable for detecting extremely small changes in refractive index, resulting in a RI figure of merit (FOM) of up to 330 RIU⁻¹ and a remarkable quality (Q)-factor of up to 1800. Furthermore, due to the stretchability of the PDMS substrate, the metasurface can be actively and continuously tuned by up to 23% strain, covering nearly 150 nm of the visible light spectrum, and its reflection color covers 103% of the sRGB. According to CIELab 1931 analysis, a distinct color change is induced for every 0.01 change in environmental RI, with an average color difference of up to 5.36, achieving ultra-high sensitivity and naked-eye discernible multi-frequency colorimetric sensing.