Silicon Nanosphere with Accessible Magnetic Hotspot

Abstract High refractive index dielectric nanoparticles supporting the magnetic dipole (MD) Mie resonance are capable of inducing strongly enhanced magnetic field at an optical frequency, and have great potential for enhancing light–matter interactions such as magnetic dipole transitions of ions and molecules. However, the magnetic hotspot is usually located inside a nanoparticle and thus the development of technology to access the hotspot remains an urgent issue. Here, a silicon (Si) nanosphere having an access hole to the magnetic hotspot is proposed. Numerical simulations for a Si nanosphere with a hole of different diameters and depths are performed. Then, a solution‐based process to dig an access hole to a Si nanosphere is developed. A spectroscopic method to analyze nanohole‐induced anisotropy of a spherical nanoantenna is also developed. Finally, in combination with numerical simulations and angle‐resolved scattering measurements of a Si nanosphere with a nanohole, it is shown that the magnetic field intensity is 100‐fold enhanced at the nanohole.