Toroidal dipolar excitations in all-dielectric nanostructures

Lei Xu,Andrey E Miroshnichenko,Marcus Cai,Reza Masoudian Saadabad

doi:10.1088/1742-6596/1461/1/012191

Lei Xu, Andrey E Miroshnichenko + Show 2 more

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https://doi.org/10.1088/1742-6596/1461/1/012191

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Abstract

We have numerically investigated toroidal dipolar excitation at optical frequencies in Si nanostructures. Our results show that, through either special structured pump illumination, or by adding an additional layer associated with geometric tuning, we are able to excite strong toroidal dipolar responses with suppressed electric dipolar excitations. These findings may further pave the way to exploit future applications of toroidal resonances including optical nonlinear enhancement, induced transparency for narrow-band filter, etc.

Highlights

The toroidal multipoles are considered as complementary set of electromagnetic sources in addition to the familiar electric and magnetic multipoles
Take Si nanodisks as an example, we numerically investigate excitations of toroidal dipolar responses in dielectric nanostrucutres through two approaches: i) using structured pump illumination composed of a radially-polarized beam in conjunction with a plane wave, and ii) adding an additional thin layer to enhance the toroidal responses and suppress the electric dipole responses through the near-field interactions
The first configuration of the proposed toroidal dipolar excitation is shown in Figure 1(a), where a focused radially-polarized (RP) beam with numerical aperture 0.86 illuminates a Si nanodisk of radius 100nm, thickness 108 nm placed at the focal point

Summary

Introduction

The toroidal multipoles are considered as complementary set of electromagnetic sources in addition to the familiar electric and magnetic multipoles. We have numerically investigated toroidal dipolar excitation at optical frequencies in Si nanostructures. Through either special structured pump illumination, or by adding an additional layer associated with geometric tuning, we are able to excite strong toroidal dipolar responses with suppressed electric dipolar excitations.

Results

Conclusion