  The global structure of the Isochrons and the corresponding Phase Response
Curves are, for the first time, investigated and numerically computed for the
fundamental photonic oscillator consisted of an Optically Injected Laser. Their
crucial role in the synchronization dynamics under a periodic modulation of the
injection beam is shown, along with their capability for providing conditions
for stable phase-locking and periodic outputs with discrete equidistant spectra
in the form of frequency combs.
