TRANSIENT AND MODULATION DYNAMICS OF A MULTIMODE FABRY-PEROT LASER

The two-mode rate equations for a laser in a Fabry-Perot cavity are st udied, taking into account the dynamics of spatial hole-burning. We pr ove analytically that each mode intensity has a transient behavior cha racterized by two damped oscillation frequencies, while the total inte nsity displays a domain where only the largest oscillation frequency r emains; this domain appears to display antiphase dynamics. These resul ts are generalized to N lasing modes. We then analyze the response of the two-mode laser to a periodic pump modulation. For small modulation depth, the two oscillation frequencies are clearly displayed as reson ances on the response curve. For deeper modulation depth, the beating of the modulation frequency and the largest internal oscillation frequ ency produces a subharmonic sequence to chaos. This chaotic domain dis appears in a crisis when it collides with the branch of stable periodi c oscillations associated with the smaller oscillation frequency which coexists with the subharmonic cascade.