AlN Self-Rolled-Up Microtube Resonators with Multimode Resonances for On-Chip Optomechanical Sensing

This digest paper reports on the first experimental demonstration of optomechanical characteristics of three-dimensional (3D) aluminum nitride (AlN) self-rolled-up membrane (S-RuM) resonators with multimode resonances transduced via optical interferometry. For a full single-turn AlN S-RuM microtube, we have identified multimode resonances in the ~1–20MHz range with quality factors Qs ~800. For an unclosed AlN microtube with a longitudinal opening, we have observed up to 20 modes in ~0.5–110 MHz with Qs up to ~1200. Modeling of cross-sectional micro-ring cavity optomechanical coupling reveals a ~3.2kHz vacuum coupling rate and ~34fN radiation pressure force, in a 7μm-diameter, 10-turn AlN microtube. Numerical calculations suggest that the AlN microtube optomechanical resonator will yield a mass responsivity of ~3.3kHz/pg at the desired loading location. Understanding of the optomechanical properties facilitates the engineering of AlN S-RuM resonators for sensitive physical detection on chip, opening new avenues in optomechanical systems for precision sensing applications.