Optomechanical actuation of graphene nanoelectromechanical systems: Does it matter where you play them?

Optomechanical actuation of two-dimensional nanoelectromechanical systems (2D NEMS) offers several advantages over conventional electrostatic drive techniques, including the potential to apply local forces that can efficiently and selectively excite high order modes with low incident power. This type of local mode control is vital for applications like all-mechanical cooling and point-mass detection. However, this potential has yet to be realized because the location dependence of the optomechanical drive has yet to be examined. Here, we utilize a scanning optical drive laser to ascertain the position dependence of the optomechanical response in a graphene 2D NEMS. We find that the induced force is tightly localized around the center of the laser spot, allowing for efficient and selective excitation of high-order modes by driving on their antinodes. We find that inducing curvature with a DC electrostatic gate voltage amplifies the optomechanical response, further improving the drive efficiency and lowering the required laser power. These results establish the local nature of the optomechanical drive in graphene, and indicate that a scanning optical drive system combined with an electrostatic gate is a best-of-both-worlds approach to actuate 2D NEMS.