High order Fano resonances and giant magnetic fields in dielectric microspheres

Zengbo Wang,Andrey A Fedyanin,Liyang Yue,Oleg V Minin,Sumei Huang,James Monks,Igor V Minin,Bing Yan,Boris Luk’Yanchuk,Rakesh Dhama

doi:10.1038/s41598-019-56783-3

Abstract

We show that weakly dissipating dielectric spheres made of materials such as glass, quartz, etc. can support high order Fano resonances associated with internal Mie modes. These resonances, happening for specific values of the size parameter, yield field-intensity enhancement factors on the order of 104–107, which can be directly obtained from analytical calculations. Associated to these “super-resonances”, we analyze the emergence of magnetic nanojets with giant magnetic fields, which might be attractive for many photonic applications.

Highlights

We show that weakly dissipating dielectric spheres made of materials such as glass, quartz, etc. can support high order Fano resonances associated with internal Mie modes
An example of such high order Fano resonances are those generated in optimized disk-ring silver plasmonic nanostructure[6]
Further progress towards higher order resonances in plasmonic nanostructures, has been limited by the large dissipation associated with metals, in the visible range

Summary

Conclusions

We reveal novel, super-resonance modes supported by dielectric spheres These resonances, present for all multipolar orders, exhibit Fano line shapes and have extraordinarily high associated electric and magnetic field enhancements, which increase linearly with the multipolar order. The phenomenon can be observed at visible frequencies using simple glass microspheres, which may allow enhancing the magnetic field of light (which is typically small) by a few orders of magnitude We believe these super-resonances are an attractive platform for some promising applications, like e.g. enhanced absorption effect, ablation caused by magnetic pressure, or those mentioned above. As a result the values of amplitudes c 2 and d 2 are not restricted by unity as amplitudes a 2 and b 2 in (2), but increase with values of size paramete r and re fractive index To compare both type of reso nances i t is convenient to introduce partial internal scattering efficiencies, like in Eq (1):.

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Additional information