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Bifurcation scenario leading to multiple pulse emission in VECSELs

Depending on the operation conditions of mode-locked semiconductor lasers different dynamical regimes exist and are well understood. However, if the amplifying and the absorbing material are embedded in a V-shaped external cavity, new multi-pulse (pulse cluster) solutions emerge. We theoretically model such a device by a system of multi-delay differential equations and apply numeric integration as well as path-continuation methods to understand the underlying bifurcation scenarios. Our investigations indicate that by repositioning the gain-chip, the laser can be operated in different stable regions e.g. fundamental, higher harmonic or multi-pulse mode-locking. Furthermore, our bifurcation analysis shows how the multi-pulse solutions evoke from the fundamental mode-locking branch and that different operation regimes can be favored by introducing an asymmetry to the cavity.