Optical Sorting of a Plasmonic Nanoparticle From a Three‐Particle Cluster Using a C‐Shaped Plasmonic Engraving

Optical sorting exploits light to separate particles by type, such as plasmonic, dielectric, or chiral, without the cost and hazard of chemical‐based methods. Here, we propose a simple gold substrate featuring an HSQ‐filled C‐shaped engraving (CSE) that selectively extracts a plasmonic Rayleigh particle from a three‐particle cluster of dielectric, plasmonic, and dielectric‐chiral particles. Under plane‐polarized incident light, a strong pushing force drives the plasmonic particle toward the center of the CSE, while the dielectric and chiral particles experience negligible force regardless of cluster composition. This selective force is explained through the Lorentz and bulk force contributions, alongside the reversal of current density within the plasmonic particle. Our COMSOL‐based numerical framework is validated against independently published results for all three particle types. A coupled electromagnetic‐thermal analysis further confirms that the proposed optical sorting force exceeds competing photothermal (thermophoretic) forces by more than five orders of magnitude under realistic illumination, even near water's absorption band. This work offers a robust, chemical‐free alternative for sorting plasmonic nanoparticles from heterogeneous clusters.