Exploitable fibre nonlinearity in coupled-cavity colour centre lasers

In experiments conducted on a synchronously mode-locked colour centre laser, significant enhancement in the mode-locking was observed when a length of optical fibre having normal group velocity dispersion (GVD) was incorporated within an external cavity. The authors show that although the fibre had normal or positive GVD and so the duration of the phase-modulated pulses is increased during propagation, these temporally broadened pulses fed back into the master cavity can lead to a narrowing of the pulses from the composite-cavity laser