Temporally Locked Exceptional Points for an Ultrasensitive Metasurface Biosensor

Non-Hermitian degeneracies, notably exceptional points (EPs), enable ultrasensitive detection via an eigenvalue topology. Nevertheless, conventional EP-based metasurface biosensors require stringent fabrication precision to attain the ideal EP state, while the detection metric is restricted to only spectral splitting. Here, we demonstrate the locking of EPs even employing two nondegenerate nanoresonators by integrating a temporal dimension into a non-Hermitian Jones matrix, in which the target nanometer-size bioanalytes induce time-dependent phase reversal associated with chirality, effectively mapping the sensing signals onto the time domain. This yields a substantially greater relative signal variation than the frequency splitting in the conventional EP sensors. Intriguingly, the proposed temporally binarized gating strategy facilitates exact subgroup classification within a wide analyte concentration range. We anticipate that the proposed temporal EP-locked biosensor platform will not only provide a compelling framework for exploring non-Hermitian optical polarization dynamics but also promise rapid, sensitive, and scalable decision-making for diverse biomarker detection.