Polarization‐Controlled Non‐Hermitian Metasurfaces for Ultra‐Sensitive Terahertz Sensing

Abstract Non‐Hermitian systems offer significant advantages in sensing technology, with most studies primarily focused on exceptional points. However, the extreme sensitivity near these points poses great challenges due to fabrication errors and system noises, which degrade sensing performance. To address this, a novel approach is introduced that leverages the polarization degrees of freedom in non‐Hermitian systems. A direct relation between the incident polarization angle and the transmission phase of a coupled metasurface system is achieved and the polarization‐controlled phase singularity even post‐fabrication is achieved. In addition, the incident polarization angle is utilized as a sensing index, which enables indirect and accurate measurement. The theoretical approach is experimentally validated using a general design of THz non‐Hermitian metasurface sensors. The method enhances robustness and sensitivity, opening new avenues for practical applications in ultra‐sensitive sensing.