Advanced control schemes for passively mode-locked lasers: Coupled lasers and dual-feedback approaches

We investigate optical control schemes for passively mode-locked lasers (PMLLs). The coupling of two identical PMLLs provides a possibility to produce highly regular pulse trains by reducing the pulse timing jitter, superior to the single optical feedback scheme, while furthermore allowing for an effective doubling of the pulse repetition rate for proper coupling delay. A dual optical feedback scheme is identified as a way to tune the repetition rate of a single PMLL over several hundred MHz while maintaining very low timing jitter.