Phase-matched metadevice for optical vortex interferometry: stable nano-displacement sensing

A highly stable nano-displacement sensing system is proposed to address key bottlenecks in high-precision optical vortex-based metrology: reliance on bulky, high-cost spatial light modulators, and vulnerability to ambient perturbations. By fabricating a flexible, compact metadevice composed of 2D subwavelength nanostructure arrays, a 4th-order vortex beam is generated without requiring a specific propagation distance. Notably, combining the topological charge with the Gaussian weighting method effectively suppresses the random errors of the petal-shaped interference pattern, thereby enhancing demodulation accuracy and stability. The sensitivity exceeds 0.05813°/nm and the linearity coefficient reaches 0.99995 within a 400 nm displacement range. Thus, the minimum uncertainty of 0.01% is achieved with a step size of 200 nm. This method demonstrates the superiority of metadevices, which serve as excellent integrated optical devices, in enabling efficient light field regulation and characterization for high-precision measurements.