Amplifier Similariton:

Overview of Evolution:

A pulse under nonlinearity, normal dispersion, and gain develops a parabolic intensity and a linear up-chirp, asymptotically approaching a self-similar evolution known as an amplifier similariton. The remainder of the cavity is relatively insignificant except that the pulse must return to its original state for the next roundtrip.

Cavity Design:

Longer, less highly doped gain fibers (typ. 2-4 m) enhance convergence to the amplifier similariton pulse shape. Normal GVD in the gain is essential, but the net cavity dispersion may take on any value, with net normal (and particularly, all-normal) cavities producing the highest energies. Each time the pulse enters the gain fiber, it must be close enough to its ultimately parabolic form to reach that shape by the end of the gain. This can be accomplished by inserting a narrowband spectral filter into the feedback loop.

Few-nJ, few-ps pulses are obtainable, which dechirp cleanly to <100 fs. Using longer cavity lengths, 15 nJ, few-hundred-fs pulses can also be produced. The output chirp depends on the exact cavity design, but in optimized cavities, is somewhat less than the cavity dispersion.

The possibility of eliminating anomalous dispersion from the cavity permits higher energies than passive similariton oscillators, while the output pulses can be dechirped somewhat more cleanly than dissipative solitons.

Pulse energy and duration are primarily limited by gain narrowing and stimulated Raman scattering, which disrupt the evolution to an amplifier similariton.

Related Papers:

1. M. E. Fermann, V. I. Kruglov, B. C. Thomsen, J. M. Dudley, and J. D. Harvey.  “Self-similar propagation and amplification of parabolic pulses in optical fibers.”  Physical Review Letters 84, 26 (2000).
2. B. Oktem, C. Ülgüdür, and F. Ö. Ilday. “Soliton-similariton fibre laser.” Nature Photonics 4, 5 (2010).
3. C. Aguergaray, D. Méchin, V. Kruglov, and J. D. Harvey. “Experimental realization of a mode-locked parabolic Raman fiber oscillator.” Optics Express 18, 8 (2010).
4. W. H. Renninger, A. Chong, and F. W. Wise.  “Self-similar pulse evolution in an all-normal-dispersion laser.”  Physical Review A 82, 2 (2010).
5. W. H. Renninger, A. Chong, and F. W. Wise.  “Amplifier similaritons in a dispersion-mapped fiber laser [Invited].”  Optics Express 19, 23 (2011).
6. B. Nie, D. Pestov, F. W. Wise, and M. Dantus. “Generation of 42-fs and 10-nJ pulses from a fiber laser with self-similar evolution in the gain segment.” Optics Express 19, 13 (2011).

Animation credit: Walter Fu.