From Fano resonances to bound states in the continuum in dipole arrays at THz frequencies

Abstract

Fano resonances and bound states in the continuum (BICs) exhibit a rich phenomenology stemming from, respectively, their asymmetric line shapes and infinite quality factors. Here, we show experimentally and theoretically that rod dimer metasurfaces exhibit narrow (high-Q) Fano resonances at THz frequencies. These resonances evolve continuously into a BIC as the rods in each dimer become identical. We demonstrate analytically that this is a universal behavior occurring in arrays of dimers consisting of detuned resonant dipoles. Fano resonances arise as a result of the interference between broad and narrow lattice dipole resonances, with high-Q factors tending to infinity in the detuning parameter space as the narrow lattice resonance becomes a BIC for identical resonant dipoles. Similar configurations can be straightforwardly envisioned throughout the electromagnetic spectrum leading to ultrahigh-Q Fano resonances and BICs of interest in photonics applications such as sensing and lasing.

6 pages, 4 figures

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• Coupled electric and magnetic dipole formulation for planar arrays of dipolar particles: metasurfaces with various electric and/or magnetic meta-atoms per unit cell
• Brewster quasi bound states in the continuum in all-dielectric metasurfaces from single magnetic-dipole resonance meta-atoms
• Interdigitated Terahertz Metamaterial Sensors: Design with the Dielectric Perturbation Theory
• Quasi-trapped modes in metasurfaces of anisotropic MoS${}_2$ nanoparticles for absorption and polarization control in the telecom optical range
• Robust Transport of the Edge Modes along the Photonic Topological Interfaces of Different Configurations
• Bound State in the Continuum Supported Asymmetric Dome-shaped Dielectric Metasurface: Crossing and Avoided Crossing of Transmission with Applications
• Analogue of collectively induced transparency in metamaterials
• Simulating Topological Robustness of Fano Resonance in Rotated Honeycomb Photonic Crystals
• Magnetic-field-induced cavity protection for intersubband polaritons