Kerr beam cleaning is a nonlinear phenomenon in graded-index multimode fiber where power flows toward the fundamental mode, generating bell-shaped output beams. Here we study beam cleaning of femtosecond pulses accompanied by gain in a multimode fiber amplifier. Mode-resolved energy measurements and numerical simulations showed that the amplifier generates beams with high fundamental mode content (greater than 30% of the overall pulse energy) for a wide range of amplification levels. Control experiments using stretched pulses that evolve without strong Kerr nonlinear effects showed a degrading beam profile, in contrast to nonlinear beam cleaning. Temporal measurements showed that seed pulse parameters have a strong effect on the amplified pulse quality. These results may influence the design of future high-performance fiber lasers and amplifiers.
The peak power performance of ultrafast fiber lasers scales with fiber mode area, but large fibers host multiple modes that are difficult to control. We demonstrate a technique for single-mode operation of highly multimode fiber based on regenerative amplification. This results in a short-pulse fiber source with, to our knowledge, an unprecedented combination of features: high gain (>55dB) with negligible amplified spontaneous emission, high pulse energy (>50µJ), good beam quality (
- NSF-PAR ID:
- 10470995
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optica
- Volume:
- 10
- Issue:
- 11
- ISSN:
- 2334-2536
- Format(s):
- Medium: X Size: Article No. 1417
- Size(s):
- ["Article No. 1417"]
- Sponsoring Org:
- National Science Foundation
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