High-sensitivity bimodal nematic liquid crystal biosensor via Airy-beam-induced polarization-switchable spin splitting

Abstract The development of ultrasensitive detection technologies with multi-parameter detection capabilities holds paramount significance for the diagnosis of early-stage diseases. In this study, an Airy beam is incident on a nematic liquid crystal/analyte/topological insulator (NLC/analyte/TI) multilayer structure. The asymmetric spin splitting is induced by the synergistic effect between the wavefront structural properties of the Airy beam and the electro-optic characteristics of NLCs. The left/right circularly polarized (LCP/RCP) states are modulated separately in longitudinal and transverse spin-splitting (LSS and TSS), thereby achieving the selective output of a single polarization state. Simultaneously regulating the surface conductivity of TIs further realizes selective modulation of the polarization state. The molecular orientation of NLCs can be precisely controlled by applying an external electric field. Thus, NLCs are categorized as either in-plane switching LC (IPS-LC) or vertically aligned LC (VA-LC), depending on the rotation direction of the principal axis in or perpendicular to the incident plane. The detection systems based on the two different orientation regulation modes construct a bimodal NLC biosensor. The sensitivity of the IPS-LC biosensor is 10 6 μm RIU − 1 for high refractive indices analytes ( 1.66 RIU − 1.662 RIU ), while the VA-LC biosensor exhibits 10 7 μm / RIU for low refractive indices targets ( 1.36 RIU − 1.41 RIU ). These findings establish a novel technological approach for cancer biomarker identification.