  Direct generation of ultrashort, transform-limited pulses in a laser
resonator is observed theoretically and experimentally. This constitutes a new
type of ultrashort pulse generation in mode-locked lasers: in contrast to the
well-known solitons (hyperbolic secant like), dispersion-managed solitons
(Gaussian-like), and parabolic pulses plus external compression, ultrashort
pulse solutions to the nonlinear wave equations that describe pulse evolution
in the laser cavity are observed. Stable ultrashort, transform-limited pulses
exist with optical spectrum broader than the gain bandwidth of the amplifier,
and this has practical application for other lasers.
