Ultra-sensitive measurement of transverse displacements with structured light

TL;DR

This paper presents a novel optical encoding method called 'linear photonic gears' that enables ultra-sensitive, non-contact measurement of transverse displacements with sub-nanometer resolution, suitable for compact sensor applications.

Contribution

Introduction of 'linear photonic gears', a new optical technique for highly precise displacement measurement using polarization rotations, with potential for integration and practical deployment.

Findings

Achieved 400 pm resolution in ambient conditions

Projected 50 pm resolution with current technology

Single-optical-path scheme offers intrinsic stability

Abstract

Accurately measuring mechanical displacements is essential for a vast portion of current technologies. Several optical techniques accomplish this task, allowing for non-contact sensing even below the diffraction limit. Here we introduce an optical encoding technique, dubbed "linear photonic gears", that enables ultra-sensitive measurements of transverse displacements by mapping these into polarization rotations of a laser beam. In ordinary ambient conditions, we measure the relative shift between two objects with a resolution of 400 pm. We argue that a resolution of 50 pm should be achievable with existing state-of-the-art technologies. Our single-optical-path scheme is intrinsically stable and it could be implemented as a compact sensor, using integrated optics. We anticipate it may have a strong impact on both research and industry.