Linewidth broadening across a dynamical instability

We investigate experimentally and theoretically the variation of the emissi on linewidth of an optically-injected semiconductor laser across a resonant period-doubling bifurcation. Close to the dynamical instability, the intri nsic and external phase fluctuations are amplified, resulting in a spectral linewidth in excess of that accounted for by the spontaneous-emission proc ess alone. (C) 1998 Elsevier Science B.V.