Scanning force sensing at $\mu$m-distances from a conductive surface with nanospheres in an optical lattice

TL;DR

This paper presents a method for trapping and maneuvering dielectric nanoparticles near a conductive surface using optical standing waves, enabling high-precision force sensing at micron-scale distances.

Contribution

It introduces a technique to position and scan nanoparticles near a metallic surface for advanced force measurements and surface interactions.

Findings

Successfully trapped and positioned nanoparticles within hundreds of nanometers to tens of microns from a gold surface.

Demonstrated two-dimensional scanning parallel to the surface using a piezo-driven mirror.

Enabled potential applications in high-sensitivity force microscopy and fundamental physics tests.

Abstract

The center-of-mass motion of optically trapped dielectric nanoparticles in vacuum is extremely well-decoupled from its environment, making a powerful tool for measurements of feeble sub-attonewton forces. We demonstrate a method to trap and manuever nanoparticles in an optical standing wave potential formed by retro-reflecting a laser beam from a metallic mirror surface. We can reliably position a $\sim 170$ nm diameter silica nanoparticle at distances of a few hundred nanometers to tens of microns from the surface of a gold-coated silicon mirror by transferring it from a single-beam tweezer trap into the standing wave potential. We can further scan the two dimensional space parallel to the mirror surface by using a piezo-driven mirror. This method enables three-dimensional scanning force sensing near surfaces using optically trapped nanoparticles, promising for high-sensitivity scanning force microscopy, tests of the Casimir effect, and tests of the gravitational inverse square law at micron scales.