  A high-finesse suspended mirror Fabry-Perot cavity is experimentally studied
in a regime where radiation pressure and photothermal effect are both relevant.
The competition between these phenomena, operating at different time scales,
produces unobserved dynamical scenarios where an initial Hopf instability is
followed by the birth of small-amplitude chaotic attractors which erratically
but deterministically trigger optical spikes. The observed dynamical regimes
are well reproduced by a detailed physical model of the system.
