# Switchable invisibility of dielectric resonators

## TL;DR

This paper demonstrates that finite dielectric resonators can achieve switchable invisibility by suppressing scattering through Fano interference, with experimental verification at microwave frequencies.

## Contribution

It reveals that finite dielectric rods with certain aspect ratios can recover invisibility, extending the concept from infinite to finite resonators, supported by experimental results.

## Key findings

- Invisibility is recoverable in finite dielectric rods with specific aspect ratios.
- Fano interference suppresses scattering in these resonators.
- Experimental verification at microwave frequencies confirms the theoretical predictions.

## Abstract

The study of invisibility of an infinite dielectric rod with high refractive index is based on the two-dimensional Mie scattering problem, and it suggests strong suppression of scattering due to the Fano interference between spectrally broad nonresonant waves and narrow Mie-resonant modes. However, when the dielectric rod has a finite extension, it becomes a resonator supporting the Fabry-Perot modes which introduce additional scattering and eventually destroy the invisibility. Here we reveal that for shorter rods with modest values of the aspect ratio r/L (where r and L are the radius and length of the rod, respectively), the lowest spectral window of the scattering suppression recovers completely, so that even a finite-size resonator may become invisible. We present a direct experimental verification of the concept of switchable invisibility at microwaves using a cylindrical finite-size resonator with high refractive index.