Sub-Diffraction Limit Quantum Metrology for Nanofabrication

Optical monitoring of object position and alignment with nanoscale precision is critical for ultra-precision measurement applications, such as micro/nano-fabrication, weak force sensing, and microscopic imaging. Traditional optical nanometry methods often rely on precision nanostructure fabrication, multi-beam interferometry, or complex post-processing algorithms, which can limit their practical use. In this study, we introduced a simplified and robust quantum measurement technique with an achievable resolution of 2.2 pm and an experimental demonstration of 1 nm resolution, distinguishing it from conventional interferometry, which depended on multiple reference beams. We designed a metasurface substrate with a mode-conversion function, in which an incident Gaussian beam is converted into higher-order transverse electromagnetic mode (TEM) modes. A theoretical analysis, including calculations of the Fisher information, demonstrated that the accuracy was maintained for nanoscale displacements. In conclusion, the study findings provide a new approach for precise alignment and metrology of nanofabrication and other advanced applications.