Spatially Resolved Optical Excitation of Mechanical Modes in Graphene NEMS

TL;DR

This paper demonstrates the use of focused optical probes to spatially resolve and selectively actuate mechanical modes in graphene NEMS, enabling precise imaging and control of high-order vibrational modes.

Contribution

It introduces a combined interferometry and optical drive technique to map forces and motion, revealing the spatial resolution of optical actuation in 2D NEMS.

Findings

Optical drive force resolution is on the order of the laser spot size.

Selective actuation of orthogonal mechanical modes is achieved.

The method enables imaging and control of arbitrary high-order modes.

Abstract

Emerging applications in nanoelectromechanical systems (NEMS) made from two-dimensional (2D) materials demand simultaneous imaging and selective actuation of the mechanical modes. Focused optical probes to measure and actuate motion offer a possible solution, but their lateral spatial resolution must be better than the size of the resonator. While optical interferometry is known to have excellent spatial resolution, the spatial resolution of the focused, laser-based optical driving is not currently known. Here, we combine separately scanned interferometry and optical drive probes to map the motion and forces on a suspended graphene nanomechanical resonator. By analyzing these maps with a force density model, we determine that the optical drive force has a spatial resolution on the order of the size of the focused laser spot. Using the optical force probe, we demonstrate the selective actuation and suppression of a pair of orthogonal, antisymmetric mechanical modes of the graphene resonator. Our results offer a powerful approach to image and actuate any arbitrary high-order mode of a 2D NEMS.