Pulse bound-state clusters in coupled mode-locked lasers

Abstract

Mode-locked semiconductor lasers are widely used for generation of short optical pulses with high repetition rates and optical frequency combs suitable for numerous practical applications. By combining many lasers into an array one can achieve much larger output power and substantially improve the characteristics of the output radiation. In this presentation we study dynamical regimes of operation in an array of mode-locked lasers locally coupled in a ring geometry. We demonstrate that unlike a solitary mode-locked laser emitting a sequence of equidistant pulses with the pulse repetition frequency close to the inverse cavity round trip time, an array of mode-locked lasers can radiate a periodic sequence of clusters of fundamental mode-locked pulses. This regime associated with the formation of closely packed bound states of coupled mode-locked pulses due to a balance between attraction and repulsion is very different from the standard harmonic mode-locked regime where the pulses always repel each other.