Critical couplings in topological-insulator waveguide-resonator systems observed in elastic waves

Abstract

Waveguides and resonators are core components in the large-scale integration of electronics, photonics, and phononics, both in existing and future scenarios. In certain situations, there is critical coupling of the two components; i.e., no energy passes through the waveguide after the incoming wave couples into the resonator. The transmission spectral characteristics resulting from this phenomenon are highly advantageous for signal filtering, switching, multiplexing, and sensing. In the present study, adopting an elastic-wave platform, we introduce topological insulator (TI), a remarkable achievement in condensed matter physics over the past decade, into a classical waveguide-ring-resonator configuration. Along with basic similarities with classical systems, a TI system has important differences and advantages, mostly owing to the spin-momentum locked transmission states at the TI boundaries. As an example, a two-port TI waveguide resonator can fundamentally eliminate upstream reflections while completely retaining useful transmission spectral characteristics, and maximize the energy in the resonator, with possible applications being novel signal processing, gyro/sensing, lasering, energy harvesting, and intense wave-matter interactions, using phonons, photons, or even electrons. The present work further enhances the confidence of using topological protection for practical device performance and functionalities, especially considering the crucial advantage of introducing (pseudo)spins to existing conventional configurations. More in-depth research on advancing phononics/photonics, especially on-chip, is foreseen.

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• Observation of phononic helical edge states in a mechanical 'topological insulator'
• Observation of topological valley transport of sound in sonic crystals
• PT-Symmetric Phonon Laser
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• Phononic band structure engineering for high-Q gigahertz surface acoustic wave resonators on lithium niobate
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• Spherical topological insulator
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Cited by in corpus (6)

• On-chip higher-order topological micromechanical metamaterials
• Nonreciprocal optical solitons in a spinning Kerr resonator
• Acoustic corner states in topological insulators with built-in Zeeman-like fields
• Floquet Mode Resonance: Trapping light in the bulk mode of a Floquet topological insulator by quantum self-interference
• Evanescently coupled topological ring-waveguide systems for chip-scale ultrahigh frequency phononic circuits
• A soft-clamped topological waveguide for phonons