Pure magnetic hotspots via hollow silicon nanoparticles illuminated by cylindrical vector beams

Abstract

Overshadowed by the electric dipole ones, the magnetic dipole transitions of a quantum emitter are hard to probe. This can be remedied by using pure magnetic hotspots, which host strong magnetic but quite weak electric fields in a subwavelength region. Utilizing the multiparticle Mie theory, we demonstrate pure magnetic hotspots via hollow silicon nanoparticles arranged in a ring configuration and illuminated by Bessel cylindrical vector beams. Normalized local field admittances of about 105–107 and magnetic field enhancements of about 10–30 are achievable. Moreover, the peak of the magnetic field enhancement can be shifted about 370 nm via the hollow size. In other words, the pure magnetic hotspot can be optimized for a particular magnetic dipole transition.