Extended Self-Similar:

Oscillators featuring extended self-similar evolution are a subset of amplifier similariton oscillators. A highly nonlinear fiber or a dispersion-decreasing fiber (DDF) is placed after the gain, maintaining the parabolic evolution and allowing the similariton to accumulate additional spectral components without bandwidth restrictions. This approach can yield nJ-level pulses with durations ~20 fs, which are some of the shortest pulses from a fiber laser to-date.

Related Papers:

1. D. Anderson, M. Desaix, M. Karlsson, M. Lisak, and M. L. Quiroga-Teixeiro. “Wave-breaking-free pulses in nonlinear-optical fibers.” Journal of the Optical Society of America B 10, 7 (1993).
2. T. Hirooka and M. Nakazawa. “Parabolic pulse generation by use of a dispersion-decreasing fiber with normal group-velocity dispersion.” Optics Letters 29, 5 (2004).
3. A. Chong, H. Liu, B. Nie, B. G. Bale, S. Wabnitz, W. H. Renninger, M. Dantus, and F. W. Wise.  “Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution.”  Optics Express 20, 13 (2012).
4. H. Liu, F. Yu, A. Chong, J. C. Knight, and F. W. Wise. “Extended self-similar pulse evolution in a laser with dispersion-decreasing fiber.” CLEO (2013).
5. Y. Tang, Z. Liu, W. Fu, and F. W. Wise. “Self-similar pulse evolution in a fiber laser with a comb-like dispersion-decreasing fiber.” Optics Letters 41, 10 (2016).