Strong Nanomechanical Duffing Nonlinearity and Interactions Induced through Cavity Optomechanics

Nonlinearity is a key resource in both classical and quantum signal processing. Nonlinear nanomechanical elements enable applications from sensing to computing, while networks of nonlinear or nonlinearly coupled resonators offer promising platforms for simulating complex dynamics. Here, we experimentally demonstrate an approach to realizing strong mechanical nonlinearity in nanomechanical resonators, which is fully controlled through optical laser drives. The mechanism exploits the intrinsic nonlinearity of the radiation pressure interaction in a cavity optomechanical system, giving rise to a nonlinear optical spring effect. The resulting Duffing nonlinearity is conveniently tunable in strength via spring laser power and in sign via detuning. Moreover, we demonstrate that the nonlinear optical spring mediates effective interactions between mechanical modes coupled to a common cavity, inducing tunable nonlinear interactions between them that impact the spectral response and dynamics. These results establish cavity optomechanics as a versatile and in situ reconfigurable platform for engineering nonlinear dynamics in resonators and networks.