Desktop laboratory of bound states in the continuum in metallic waveguide with dielectric cavities

TL;DR

This paper introduces a practical dielectric cavity system within a metallic waveguide that supports various bound states in the continuum, including topological BICs, with enhanced Q-factors, facilitating experimental investigations.

Contribution

It presents a finite, experimentally accessible dielectric cavity system supporting diverse BICs, including topological ones, with improved Q-factors due to merging effects.

Findings

Supports topological BICs with adjustable position and orientation.

Achieves high Q-factors with power-law scaling up to 6.

Facilitates experimental study of BICs in finite systems.

Abstract

We consider dielectric cavities whose radiation space is restricted by two parallel metallic planes. The TM solutions of the Maxwell equations of the system are equivalent to the solutions of periodical arrays of dielectric cavities. The system readily allows to achieve bound states in the continuum (BICs) of any type including topological BICs as dependent on position and orientation of the cavities relative to the planes. That extremely facilitates experimental studies in comparison to infinite arrays of the cavities. We show the effect of merging of topologically protected BICs that pushes the square asymptotic of the $Q$-factor into the power degree 4 or even 6.