  We report theoretical and experimental evidence of chaotic pulses with
excitable-like properties in an opto-radiofrequency oscillator based on a
self-injected dual-frequency laser. The chaotic attractor involved in the
dynamics produces pulses that, albeit chaotic, are quite regular: They all have
similar amplitudes, and are almost periodic in time. Thanks to these features,
the system displays properties that are similar to those of excitable systems.
In particular, the pulses exhibit a threshold-like response, of well-defined
amplitude, to perturbations, and it appears possible to define a refractory
time. At variance with excitability in injected lasers, here the excitable-like
pulses are not accompanied by phase slips.
