Nanoparticle Deep-Subwavelength Dynamics Empowered by Optical Meron–Antimeron Topology

Abstract

Optical meron is a type of nonplanar topological texture mainly observed in surface plasmon polaritons and highly symmetric points of photonic crystals in the reciprocal space. Here, we report Poynting-vector merons formed at the real space of a photonic crystal for a Γ-point illumination. Optical merons can be utilized for subwavelength-resolution manipulation of nanoparticles, resembling a topological Hall effect on electrons via magnetic merons. In particular, staggered merons and antimerons impose strong radiation pressure on large gold nanoparticles (AuNPs), while focused hot spots in antimerons generate dominant optical gradient forces on small AuNPs. Synergistically, differently sized AuNPs in a still environment can be trapped or orbit in opposite directions, mimicking a coupled galaxy system. They can also be separated with a 10 nm precision when applying a flow velocity of >1 mm/s. Our study unravels a novel way to exploit topological textures for optical manipulation with deep-subwavelength precision and switchable topology in a lossless environment.

Mapping Optical Lateral Forces on the Poincaré Sphere

“…A velocity of 4.5 × 10 –4 μm/s for a 200 nm-radius particle can be expected in water as predicted using the equation F = 6πη va , where η is the viscosity of the liquid, v and a are the velocity and radius of the particle, respectively. This OLF can be greater on chiral particles by the interaction of light and chirality. , Moreover, efforts can be devoted to enhance the OLF by multipoles and special light fields to enable potential applications in optical sorting . Albeit various enhancement strategies, ,− it is crucial to explore deeply how light intrinsic properties affect the OLF .…”

Robotic Nanomanipulation Based on Spatiotemporal Modulation of Optical Gradients

“…The development and integration of robotic manipulation inside a real-time imaging and characterization platform facilitate a wide range of applications in nanophotonics, nanoelectronics, and biomedicine. − Among various manipulation techniques, − optical tweezers have attracted considerable attentions for their capacity of controlling the position and orientation of single free-standing nanostructures − (e.g., nanorod and nanowire) and selective deposition (i.e., direct laser printing) of these nanostructures in targeted positions with high precision. − Equipped with a feedback-controlled interface, optical tweezers can be turned into a versatile robotic manipulation platform, which is highly desirable for the development of optical manipulation combined with microscopy/spectroscopy. ,, Specifically, unlike automated manipulation, which demands sophisticated algorithms for planning, decision-making, and fault-tolerance handling, human-in-the-loop control proves to be equally compelling, particularly in scenarios that necessitate substantial human involvement; for example, optical manipulation of functional NPs for active drug delivery and nanosurgery in complex fluidic environments, e.g., blood vessels and neural network. Customizable route planning through a human–machine interface (HMI) is more feasible. − …”