Speaker
Description
Monitoring of the absorption of microwaves in water-laden food is commonly established with thermal imaging, the potential of using thermography for visualizing electromagnetic concentration in resonant aqueous objects has largely been overlooked. Water exhibits a remarkably high refractive index on the order of n~9 at household microwave frequencies of 2.5 GHz. In these systems, the comparable wavelength-to-particle size ratio facilitates the trapping of electromagnetic waves, creating highly localized energy distributions, turning grape-sized water spheres into dielectric Mie resonators that are known to spark impressively in microwave ovens. A modest amount of absorption is advantageous as it generates a measurable thermal response without unduly disrupting the underlying resonant character. Consequently, the localized internal electric field patterns can then be captured as distinct temperature gradients. In this presentation, we introduce a novel methodology for visualizing these internal electromagnetic resonances using thermal imaging. We then show excellent comparison between simulated electric-filed mode maps and temperature distributions in isolated objects such as grapes and hydrogel beads at the fundamental magnetic dipole and electric dipole resonant sizes. Finally, we extend this approach to study mode evolution during sphere dimerization, showing how thermal patterns can be used as a reliable proxy for investigating complex photonic coupling effects. Ultimately, our approach provides a macroscopic tool for visualizing photonic effects that would be impossible to image in nanoparticle analogs.
