Deployable Nanoelectromechanical Bound States in the Continuum Enabled by GHz Lamb Wave Phononic Crystals on LiNbO3 Thin Films

TL;DR

This paper demonstrates scalable, deployable nanoelectromechanical quasi-BICs on LiNbO3 thin films using GHz Lamb wave phononic crystals, enabling efficient excitation and multiplexing for advanced applications.

Contribution

It introduces a practical method to realize high-Q BICs in nanoelectromechanical systems through symmetry breaking and Lamb wave mode decoupling, facilitating on-chip integration.

Findings

Achieved high-Q quasi-BICs at gigahertz frequencies on LiNbO3 films.

Enabled excitation of BICs by traveling waves without specialized schemes.

Demonstrated multiplexing of resonators along a single transmission line.

Abstract

Bound states in the continuum (BICs) are a fascinating class of eigenstates that trap energy within the continuum, enabling breakthroughs in ultra-low-threshold lasing, high-Q sensing, and advanced wave-matter interactions. However, their stringent symmetry requirements hinder practical integration, especially in acoustic and electromechanical systems where efficient mode excitation is challenging. Here, we demonstrate deployable nanoelectromechanical quasi-BICs on suspended lithium niobate (LiNbO3) thin films, enabled by nanoscale Lamb wave phononic crystals (PnCs) operating at gigahertz frequencies. By exploiting the decoupling of symmetric (S) and antisymmetric (A) Lamb wave modes, we create a robust framework for BICs. Controlled mirror symmetry breaking induces targeted coupling between the S and A modes, resulting in quasi-BICs that preserve high-Q characteristics and can be excited by traveling waves, eliminating the need for specialized excitation schemes. Our approach enables the multiplexing of quasi-BIC resonators along a single transmission line, each corresponding to a unique frequency and spatial position. This work presents a scalable route for the on-chip integration of BICs, bridging the gap between theoretical concepts and practical nanoelectromechanical devices, and opening new avenues in advanced signal processing, high-precision sensing, and quantum acoustics.