  Chaos has revolutionized the field of nonlinear science and stimulated
foundational studies from neural networks, extreme event statistics, to physics
of electron transport. Recent studies in cavity optomechanics provide a new
platform to uncover quintessential architectures of chaos generation and the
underlying physics. Here we report the generation of dynamical chaos in
silicon-based monolithic optomechanical oscillators, enabled by the strong and
coupled nonlinearities of two-photon-absorption induced Drude electron-hole
plasma. Deterministic chaotic oscillation is achieved, and statistical and
entropic characterization quantifies the chaos complexity at 60 fJ intracavity
energies. The correlation dimension D2 is determined at 1.67 for the chaotic
attractor, along with maximal Lyapunov exponent rate about 2.94 the fundamental
optomechanical oscillation for fast adjacent trajectory divergence. Nonlinear
dynamical maps demonstrate the subharmonics, bifurcations, and stable regimes,
along with distinct transitional routes into chaos. This provides a
CMOS-compatible and scalable architecture for understanding complex dynamics on
the mesoscopic scale.
