# Lateral Optical Forces on Linearly-Polarized Emitters near a Reciprocal Substrate

## TL;DR

This paper theoretically explores lateral optical forces on dipole emitters near reciprocal substrates, revealing conditions under which such forces vanish or appear, especially highlighting a novel recoil force for combined electric and magnetic dipoles near tilted uniaxial dielectrics.

## Contribution

It demonstrates that linearly polarized electric dipoles experience no lateral force near reciprocal substrates, but a superposition of electric and magnetic dipoles can induce a recoil force in specific anisotropic conditions.

## Key findings

- Lateral forces vanish for linearly polarized electric dipoles near reciprocal substrates.
- A recoil force can occur for combined electric and magnetic dipoles near tilted uniaxial dielectrics.
- Recoil force is oriented perpendicular to the interface normal and substrate optical axis.

## Abstract

We theoretically investigate the emergence of lateral (recoil) forces acting on generic dipole-type emitters in the vicinity of a reciprocal translation-invariant substrate. Surprisingly, we find that for linearly-polarized electric dipoles the lateral force invariably vanishes, independent of the anisotropy (e.g., tilted optical axes) or chirality of the substrate. We identify a novel opportunity to have a recoil force relying on a superposition of two linearly-polarized and collinear electric and magnetic dipoles. Counterintuitively, it is shown that when such an emitter stands above a uniaxial dielectric half-space with tilted optical axes it may experience a recoil force oriented along the direction perpendicular to the plane defined by the interface normal and the substrate optical axis.

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Source: https://tomesphere.com/paper/1901.11089