| dc.description | Passively mode-locked fiber lasers are versatile and low-cost sources of ultrashort pulses that are
attractive for applications. Although initially developed for the generation of extremely short, subpicosecond
pulses, these lasers are now also used for the production of longer pulses with very high
energies, in particular in the normal dispersion regime [1].
Recently, a novel category of pulses, the noise-like pulses [2-6], have attracted a lot of interest because of
their high energy, wide spectrum (potentially beyond 100 nm [4]) and low coherence length, which
makes them attractive for important applications such as supercontinuum generation [7] and sensing [8],
among others. Fundamentally, a noise-like pulse is a large, ~ns collection of thousands of ultrashort (subps)
pulses with randomly varying amplitudes and durations that are packed together. Although the details
of the inner pulses are extremely variable in time, the global properties of the noise-like pulse, like its
overall duration, average inner pulse duration and spectral width remain constant, so that in a sense noiselike
pulsing can still be seen as a stable mode-locking regime. In practice, the noise-like pulsing regime is
easily recognized by its double-scaled autocorrelation trace, with a narrow coherence peak riding a wide
and smooth pedestal, and by a very smooth optical spectrum. These two basic signatures of this particular
mode locking regime are found with very few variations in the literature, in both normal and anomalousdispersion
cavities.
In this work, we show experimentally that, in spite of this apparent uniformity, two distinct regimes can
be distinguished in a passively mode-locked fiber laser, each of them leading to the formation of noiselike
pulses but with different properties. | |
