Analysis of nanomechanical motion detection method based on optical knife-edge effect

Abstract A moving edge of a small mechanical structure, closely placed in front of a photodetector, can offer an easy means of monitoring its motion via the optical knife-edge effect. Here, we present a detailed analysis of this nanomechanical motion detection scheme, in which the miniaturized mechanical device to be probed also serves as an effective knife edge. Especially the optical modulation generated from the expected motion of the mechanical structure as well as the corresponding detection sensitivity is considered by analytical and numerical modeling along with the experimental observation in light of the relevant key factors such as the optical spot size and the device dimension. The results discussed would benefit further implementation of the compact optical detection scheme demonstrated.