Dynamics and coherence of a multimode semiconductor laser with optical feedback in an intermediate-length external-cavity regime

Departament de Fi´sica i Enginyeria Nuclear, Universitat Polite`cnica de Catalunya, Colom 1, E-08222 Terrassa, Spain~Received 26 February 2003; published 4 November 2003!We use a traveling-wave numerical model of the temporal dynamics in semiconductor lasers to investigatethe dynamics and coherence properties of a multimode semiconductor laser subject to optical feedback. Con-sidering an external cavity of intermediate length, we have observed features characteristic of the so-calledshort-cavityregime in a region where the relaxation oscillations frequency is larger than the external-cavityfrequency. The time scales of the dynamics are controlled in this case by the strength of the optical feedback.We have examined the coherence properties of the multimode emission and have studied how the coherencetime is reduced as the laser becomes more multimode.DOI: 10.1103/PhysRevA.68.053804 PACS number~s!: 42.65.Sf, 05.45.Jn, 42.55.PxI. INTRODUCTION