Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices

Felix Kronowetter; Marcus Maeder; Yan Kei Chiang; Lujun Huang; Johannes D Schmid; Sebastian Oberst; David A Powell; Steffen Marburg

doi:10.1038/s41467-023-42621-8

Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices

Nat Commun. 2023 Oct 27;14(1):6847. doi: 10.1038/s41467-023-42621-8.

Authors

Felix Kronowetter^{1

2

3}, Marcus Maeder⁴, Yan Kei Chiang⁵, Lujun Huang⁵, Johannes D Schmid⁴, Sebastian Oberst⁶, David A Powell⁵, Steffen Marburg⁴

Affiliations

¹ Chair of Vibro-Acoustics of Vehicles and Machines, Department of Engineering Physics and Computation, TUM School of Engineering and Design, Technical University of Munich, Bavaria, Germany. felix.kronowetter@tum.de.
² School of Engineering and Information Technology, University of New South Wales, Northcott Drive, Canberra, ACT, 2600, Australia. felix.kronowetter@tum.de.
³ School of Mechanical and Mechatronic Engineering, Centre for Audio, Acoustics and Vibration, Faculty of Engineering and IT, University of Technology Sydney, Sydney, Australia. felix.kronowetter@tum.de.
⁴ Chair of Vibro-Acoustics of Vehicles and Machines, Department of Engineering Physics and Computation, TUM School of Engineering and Design, Technical University of Munich, Bavaria, Germany.
⁵ School of Engineering and Information Technology, University of New South Wales, Northcott Drive, Canberra, ACT, 2600, Australia.
⁶ School of Mechanical and Mechatronic Engineering, Centre for Audio, Acoustics and Vibration, Faculty of Engineering and IT, University of Technology Sydney, Sydney, Australia.

Abstract

Quasi-bound states in the continuum (QBICs) coupling into the propagating spectrum manifest themselves as high-quality factor (Q) modes susceptible to perturbations. This poses a challenge in predicting stable Fano resonances for realistic applications. Besides, where and when the maximum field enhancement occurs in real acoustic devices remains elusive. In this work, we theoretically predict and experimentally demonstrate the existence of a Friedrich-Wintgen BIC in an open acoustic cavity. We provide direct evidence for a QBIC by mapping the pressure field inside the cavity using a Laser Doppler Vibrometer (LDV), which provides the missing field enhancement data. Furthermore, we design a symmetry-reduced BIC and achieve field enhancement by a factor of about three compared to the original cavity. LDV measurements are a promising technique for obtaining high-Q modes' missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high-intensity sound sources, filters, and sensors.