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Pure toroidal dipole in a single dielectric disk.
Optics Express
|October 15, 2022
Summary
Researchers demonstrate a pure toroidal dipole response using a simple dielectric disk, overcoming challenges of complex structures and unwanted multipoles for novel light-matter interactions.
Area of Science:
- Electromagnetism
- Dielectric Metamaterials
- Nanophotonics
Background:
- Toroidal dipoles exhibit unique radiation characteristics but are difficult to realize due to complex structures and interference from other multipoles.
- Conventional methods for achieving toroidal moments often involve intricate designs and are susceptible to unwanted electromagnetic resonances.
Purpose of the Study:
- To explore the electromagnetic properties of a simple dielectric disk under a focused radially polarized beam.
- To demonstrate a pure toroidal dipolar response and suppress other electromagnetic multipolar resonances.
- To investigate anapole modes and structural transformations for advanced light-matter interactions.
Main Methods:
- Illumination of a simple dielectric disk with a focused radially polarized beam.
- Step-by-step suppression of undesirable electromagnetic multipolar resonances.
- Optimization of disk geometry for an all-dielectric electric mirror.
- Introduction of structural and incidence asymmetry to observe mode transformations.
Main Results:
- A pure toroidal dipolar response was achieved in a simple dielectric disk.
- An all-dielectric electric mirror dominated by toroidal dipolar resonance was constructed.
- Two types of anapole modes, demonstrating electric and magnetic non-radiating sources, were investigated.
- A transformation from Mie-type to trapped modes was observed by introducing asymmetry.
Conclusions:
- The study successfully demonstrates a pure toroidal dipole in a simplified structure.
- The findings offer a pathway for realizing unique toroidal dipoles and enhancing light-matter interactions.
- The investigated anapole modes and mode transformations open possibilities for novel optical devices.
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