Optimal beam-displacement measurements using high-order structured light modes
Phys. Rev. Applied 24, 024054 – Published 21 August, 2025
DOI: https://doi.org/10.1103/b3hp-17rj
Abstract
We develop a technique to measure small angular and lateral displacements of structured light beams. The technique relies on using high-order Hermite-Gaussian (HG) and Laguerre-Gaussian (LG) modes, which have well-defined symmetry under inversion. We show that the displacements of such fields lead to crosstalk with modes with opposite parity under inversion, which we measure optimally with an interferometric parity sorter. Using this technique, we achieve improvement factors of up to 41 in the signal-to-noise ratio using HG modes and 21 using LG modes with order up to 20, as compared to the fundamental Gaussian mode. Our results present a viable way of using structured light for metrology that does not demand quantum light or homodyne detection.
