Mechanical Kerr Nonlinearity of Wave Propagation in an On-Chip Nanoelectromechanical Waveguide

We experimentally and numerically demonstrate nonlinear flexural wave propagation using an on-chip nanoelectromechanical waveguide. More specifically, third-order nonlinear phenomena of self-phase modulation, cross-phase modulation, and four-wave mixing caused by the mechanical Kerr effect are realized. Our experimental observations are correctly described by the nonlinear Schr\"odinger equation. The nanomechanical and integratable platform enables on-chip manipulation of mechanical wave propagation, thus offering the potential to develop novel functional devices and study nonlinear mechanical phenomena.