Harnessing exceptional surfaces to enhance magnetic field sensing in a microcavity

Magnetic fields are an indispensable physical quantity in high-precision detection. The exceptional surface (ES) exhibits distinct advantages in robustness and frequency splitting enhancement, providing a powerful approach for high-precision magnetic field detection. However, the ES-based microcavity suffers from inherent limitations that constrain its practicality in real-world sensing applications. Here, we proposed a novel magnetic sensing structure consisting of an add-drop microcavity and a sensing unit, which overcomes the fundamental limitation that the conventional ES-based microcavity cannot directly detect magnetic fields. The emergence of an ES significantly enhances the frequency splitting response of the transmission spectrum to external magnetic fields. Moreover, we have demonstrated that monitoring the peak intensity of the Fano line shape further improves the detection limit of the proposed sensing structure, thereby breaking through the inherent mode linewidth limitation of ES-based microcavities. This work opens new avenues for high-precision non-Hermitian magnetic sensors.