# Controlling the sign of optical forces using metaoptics

## TL;DR

Researchers use metaoptics to control whether light pushes or pulls tiny objects, enabling new ways to manipulate nanoscale systems.

## Contribution

Deterministic control of optical force sign using engineered metasurfaces in a phase-controlled standing wave.

## Key findings

- Metasurface designs enable both attractive and repulsive optical forces.
- Experimental results align with 3D simulations of multipolar mode interference.
- Platform supports optical manipulation of nanoscale mechanical systems.

## Abstract

Precise manipulation of small objects using light holds transformative potential across diverse fields. While research in optical trapping and manipulation predominantly relies on the attraction of solid matter to light intensity maxima, here we demonstrate that meta-optics enables a departure from this accepted behavior. Specifically, we present deterministic control over the sign of optical forces exerted on a metasurface integrated on a suspended silicon nanomembrane. By tailoring the geometry of the constituent meta-atoms, we engineer the coherent superposition of their multipolar modes, and consequently, the net optical force experienced by the metasurface within a phase-controlled optical standing wave. In excellent agreement with 3D numerical simulations, we experimentally realize both attractive and repulsive forces on distinct metasurface designs, directly mirroring the behavior of two-level systems interacting with optical fields. This work establishes a versatile platform for the optical control of nanoscale mechanical systems, opening alternative avenues for both fundamental research and engineering.

The authors demonstrate deterministic control of optical forces on a metasurface integrated with a suspended silicon nanomembrane. By tailoring multipolar mode interference, they realize both attractive and repulsive forces in a phase-controlled standing wave, experimentally validated, paving the way for advanced optical manipulation in nanoscale optomechanics.