Zhaoxiang Zhu, Jiaqi Li, Lixun Wu, Xin Gu, Yanfeng Zhang, Yuanhui Wen, Yujie Chen, Siyuan Yu
Breaking the half-wavelength (λ/2) sensitivity ceiling marks a decisive advance in optical displacement sensing. A sensor’s resolution is jointly determined by the sensitivity of the sensing element and the performance of the electronic interpolator. Here, we demonstrate a high-resolution displacement measurement scheme based on the photonic spin Hall effect (PSHE) implemented by a spin-dependent metasurface. Transverse displacement of the metasurface encodes the Pancharatnam–Berry phase into circularly polarized light of opposite handedness, which is then coherently superposed to form a linearly polarized output. The polarization angle of this light beam varies linearly with displacement, and by setting the analyzers, we obtain two output signals with a π/4 providing intrinsic subwavelength sensitivity. Augmented by a particle swarm optimization (PSO) algorithm for output signal correction and adaptive filter-passband selection, our sensor system surpasses the half-wavelength level sensitivity limit and achieves a displacement resolution of 116 pm (approximately λ/13,362). This work thus provides a high-resolution and broadly applicable strategy for ultra-precision metrology.