FinLN: 3D Fin Lithium Niobate Acoustic Resonators

TL;DR

This paper introduces a 3D fin lithium niobate acoustic resonator that offers enhanced electromechanical coupling and confinement, demonstrating promising performance for RF MEMS and optomechanical applications.

Contribution

The work presents the first fabrication and demonstration of a 3D FinLN acoustic resonator with significantly improved coupling over planar designs.

Findings

Operates near 300 MHz with a Q of 430

Achieves 6.2% electromechanical coupling coefficient

Provides 1.8x enhancement compared to planar resonators

Abstract

We demonstrate a three-dimensional fin lithium niobate (FinLN) acoustic resonator fabricated from thick lithium niobate on insulator using deep ion etching and sidewall electrode patterning. The FinLN geometry enables strong three-dimensional acoustic confinement and enhanced electromechanical coupling while maintaining a compact device footprint. The fabricated devices operate near 300 MHz and exhibit an effective electromechanical coupling coefficient of 6.2% with a mechanical quality factor of 430, in good agreement with finite-element simulations. Compared to planar surface acoustic wave resonators fabricated on the same wafer, the FinLN configuration achieves an 1.8x enhancement in effective coupling. This work establishes FinLN as a promising platform for compact, high-performance RF MEMS and piezo-optomechanical systems.