Mapping the multi-component of near fields using nanoparticles
Near-field optics primarily investigates optical phenomena that occur in the near-field region,defined as being within the wavelength of light.This discipline explores the interaction between light and matter at the nanoscale.Unique physical phenomena,such as spin-orbit coupling,emerge in this region,making it a significant area of research in optics.Accurate characterization of these phenomena is crucial for further exploration.However,challenges arise due to the strong confinement and the complex vector nature of near fields.Traditional near-field scanning optical microscopy employs a near-field probe to access this region and collect information about near-field light.While this approach partially addresses the confinement issue,the intricate vector nature of the near fields necessitates specially designed probes to detect various components of near fields.These probes require nanoscale structural designs and complex,expensive semiconductor fabrication processes.This paper focuses on a series of studies utilizing nanoparticles as near-field probes for multi-component characterization of optical near fields.Being spherically symmetric structures,nanoparticles can theoretically respond to all near-field components.Mie scattering theory enables us to characterize the desired near-field components,including in-plane and out-of-plane electric and magnetic fields,by choosing appropriate materials and sizes for the particles.Furthermore,precise measurements of these components allow for accurate characterization of spin components,orbital-spin coupling,and optical topological structures in the near-field region.The probes developed in this approach are easy to fabricate,cost-effective,and do not require complex control systems,providing an efficient method for research in near-field optics.
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