Enhanced spectral breathing for sub-25 fs pulse generation in a Yb-fiber laser.

We demonstrate a dispersion-mapped Yb-fiber laser with enhanced intracavity spectral breathing. A staged filtering by dissipation through a 30 nm bandpass filter and nonlinear spectral compression results in a transform-limited narrow bandwidth seed pulse for the amplifier fiber. The pulse evolves in the active fiber without gain bandwidth limitation. Further spectral scaling is achieved by single mode fiber. Simulation predicts an overall spectral breathing ratio of as high as 40. Pulse duration of sub-25 fs with 2.3 nJ pulse energy was achieved in experiment.