  While the performance of mode-locked fiber lasers has been improved
significantly, the limited gain bandwidth restricts them to generate ultrashort
pulses approaching a few cycles or even shorter. Here we present a novel method
to achieve few cycle pulses (~5 cycles) with ultra-broad spectrum (~400 nm). To
our best knowledge, this is the shortest pulse width and broadest spectrum
directly generated from fiber lasers. It is noteworthy that a dramatic
ultrashort pulse evolution can be stabilized in a laser oscillator by the
unique nonlinear processes of a self-similar evolution as a nonlinear attractor
in the gain fiber and a perfect saturable absorber action of the Mamyshev
oscillator.
