Matter manipulation with optical forces has become commonplace in a wide range of research fields and is epitomized by the optical trap. Calculations of optical forces on small illuminated particles typically neglect multiple scattering on nearby structures. However, this scattering can result in large recoil forces, particularly when the scattering includes directional near-field excitations. Nearfield recoil forces have been studied in the case of electric, magnetic and circularly polarized dipoles, but they exist for any type of directional near-field excitation. We use the force angular spectrum as a concise and intuitive analytical expression for the force on any dipole near planar surfaces, which allows us to clearly distinguish the effect due to the dipole, and due to the surface. We relate this directly to the coupling efficiency of surface or guided modes via Fermi's golden rule. To exemplify this, a near-field force transverse to the illumination is computationally calculated for a Huygens dipole near a metallic waveguide. We believe this formalism will prove insightful for various nanomanipulation systems within areas such as nanofluidics, sensing, biotechnology and nano-assembly of nanostructures. arXiv:1811.05237v3 [physics.optics]

Study of photonic spin-orbital interactions, which involves control of the propagation and spatial distributions of light with the polarization of electromagnetic fields, is not only important at the fundamental level but also has significant implications for functional photonic applications that require active tuning of directional light propagation. Many of the experimental demonstrations have been attributed to the spin-momentum locking characteristic of evanescent waves. In this letter, we show another property of evanescent waves: the polarization dependent direction of the imaginary part of the Poynting vector, i.e. reactive power. Based on this property, we propose a simple and robust way to tune the directional far-field scattering from nanoparticles near a surface under evanescent wave illumination by controlling linear polarization and direction of the incident light.

Photonics is currently undergoing an era of miniaturization thanks in part to two-dimensional (2D) optical metasurfaces. Their ability to sculpt and redirect optical momentum can give rise to an optical force, which acts orthogonally to the direction of light propagation. Powered by a single unfocused light beam, these lateral optical forces (LOFs) can be used to drive advanced metavehicles and are controlled via the incident beam’s polarization. However, the full control of a metavehicle on a 2D plane (i.e. forward, backward, left, and right) with a sign-switchable LOF remains a challenge. Here we present a phase-gradient metasurface route for achieving such full control while also increasing efficiency. The proposed metasurface is able to deflect a normally incident plane wave in a traverse direction by modulating the plane wave’s polarization, and results in a sign-switchable recoil LOF. When applied to a metavehicle, this LOF enables a level of motion control that was previously unobtainable.

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