Photoacoustic Characterization of Nanoelectromechanical Systems

A photoacoustic microscopy system has been developed to study the nanomechanical properties of Nanoelectromechanical Systems (NEMS). In these experiments, the fundamental flexural resonances of doubly-clamped nanomechanical beams are excited photo-thermally and the resulting displacements are detected using optical interferometry. Our system uses an amplified electroabsorption modulated laser source, and allows excitation at frequencies up to 5 GHz. Femtometer scale displacements of NEMS are detectable using a path-stabilized Michelson interferometer and narrowband phase sensitive detection techniques. Our measurements have enabled the determination of resonance parameters such as resonance frequencies and mechanical quality ($Q)$ factors, elastic constants and mode shapes. The results are compared to a theoretical model for photothermal excitation of doubly clamped beams. Our measurements indicate that photoacoustic microscopy is well suited for the nondestructive evaluation and opto-mechanical operation (actuation and transduction) of NEMS. This project is supported by the NSF under grant No. 0304446.