Large-range angstrom-resolution displacement sensor based on wavelength modulation capable of fiber-end integration.

Optical displacement sensors play a pivotal role in advanced manufacturing and micro-nano research, owing to their non-contact nature and superior precision. While optical fiber sensors are widely adopted for their robustness in harsh environments, they often suffer from limited sensing precision. Furthermore, existing high-precision optical sensors typically rely on intensity distribution or polarization modulation, making them incompatible with integrated fiber-optic systems. Herein, we propose a high-precision displacement sensor based on wavelength modulation capable of fiber-end integration. Firstly, a nano-slit was fabricated on a gold-coated glass coverslip. By illuminating the nano-slit with periodic dispersive interference fringes generated via white-light dual-beam interference, the displacement of the device induces a regular shift in the spectral peaks and dips of the transmission output, thereby enabling precise displacement sensing. Experimentally, the device demonstrates a maximum resolution of 0.534 nm. Moreover, by leveraging multiple interference orders within a free-space-illuminated and fiber-collected architecture, we achieved a measurement range of 820 nm. This work presents a viable pathway toward optical fiber displacement sensors featuring both high precision and a large dynamic range.