Observation of radio-frequency Mie resonances in high-permittivity dielectric spheres

Abstract

We investigate Mie resonances in a high-permittivity dielectric (ceramic) sphere within the radio-frequency (RF) range, exploring its potential application in magnetic resonance imaging (MRI). Using a transmitting and a receiving RF coil, we observe Mie resonance signatures in both the transmission frequency spectrum and the magnetic field distribution surrounding a 40 mm-diameter sphere. Through full-wave numerical simulations and a standard fitting technique, we identify and characterize the lowest-frequency transverse-electric resonance modes of the sphere at 141.6, 201.4, 259.6, and 282.6 MHz, each exhibiting high-quality factors (300). Remarkably, we experimentally map the magnetic field distributions corresponding to each Mie resonance. Our results provide valuable insights for developing innovative approaches to manipulate RF waves, particularly by shaping and controlling the near-field outside the dielectric resonator through Mie resonances, an area largely unexplored in MRI technology.