  In this work, we experimentally investigate the dynamics of pairs of
opto-thermally driven, mechanically coupled, doubly clamped, silicon
micromechanical oscillators, and numerically investigate the dynamics of the
corresponding lumped-parameter model. Coupled limit cycle oscillators exhibit
striking nonlinear dynamics and bifurcations in response to variations in
system parameters. We show that the input laser power influences the frequency
detuning between two non-identical oscillators. As the laser power is varied,
different regimes of oscillations such as the synchronized state, the drift
state, and the quasi-periodic state are mapped at minimal and high coupling
strengths. For non-identical oscillators, coexistence of two states, the
synchronized state and the quasi-periodic state, is demonstrated at high
coupling and high laser power. Experimentally, this bistability manifests as
irregular oscillations as the system rapidly switches between the two states
due to the system's sensitive dependence on initial conditions in the presence
of noise. We provide a qualitative comparison of the experimental and numerical
results to elucidate the behavior of the system.
