  Silicon on insulator photonics has offered a versatile platform for the
recent development of integrated optomechanical circuits. However, there are
some constraints such as the high cost of the wafers and limitation to a single
physical device level. In the present work we investigate nanocrystalline
silicon as an alternative material for optomechanical devices. In particular,
we demonstrate that optomechanical crystal cavities fabricated of
nanocrystalline silicon have optical and mechanical properties enabling
non-linear dynamical behaviour and effects such as
thermo-optic/free-carrier-dispersion self-pulsing, phonon lasing and chaos, all
at low input laser power and with typical frequencies as high as 0.3 GHz.
