Thermal-recovery of modal instability in rod fiber amplifiers

Mette Marie Jørgensen, Marko Laurila, Danny Noordegraaf, Thomas Tanggaard Alkeskjold, Jesper Lægsgaard

Research output: Contribution to journalConference articleResearchpeer-review


We investigate the temporal dynamics of Modal instabilities (MI) in ROD fiber amplifiers using a 100 μm core rod fiber in a single-pass amplifier configuration, and we achieve ~200W of extracted output power before the onset of MI. Above the MI threshold, we investigate the temporal dynamics of beam fluctuations in both the transient and chaotic regime. We identify a set of discrete frequencies in the transient regime and a white distribution of frequencies in the chaotic regime. We test three identical rods using a multiple ramp-up procedure, where each rod is tested in three test series and thermally annealed between each test series. We find that the MI threshold degrades as it is reached multiple times, but is recovered by thermal annealing. We also find that the test history of the rods affects the temporal dynamics.
Original languageEnglish
JournalProceedings of SPIE, the International Society for Optical Engineering
Pages (from-to)86010U
Number of pages8
Publication statusPublished - 2013
EventSPIE Photonics West : Fiber Lasers X: Technology, Systems, and Applications: Technology, Systems, and Applications - San Francisco, CA, United States
Duration: 4 Feb 20137 Feb 2013
Conference number: 10


ConferenceSPIE Photonics West : Fiber Lasers X: Technology, Systems, and Applications
CountryUnited States
CitySan Francisco, CA


  • Fiber amplifiers
  • Modal instability
  • Microstructured fibers
  • High power amplifiers
  • Photodarkening

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