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@PHDTHESIS{Liu:316801,
      author       = {Liu, Wei},
      title        = {{A}dvanced ultrafast fiber laser sources enabled by fiber
                      nonlinearities},
      school       = {Universität Hamburg},
      type         = {Dr.},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2017-00199, DESY-THESIS-2017-020},
      series       = {DESY-THESIS},
      pages        = {132},
      year         = {2017},
      note         = {Universität Hamburg, Diss., 2016},
      abstract     = {Development of high power/energy ultrafast fiber lasers for
                      scientific research and industrial applications is one of
                      the most exciting fields in ultrafast optics. This thesis
                      demonstrated newmeans to improve two essential
                      properties—which are indispensable for novel applications
                      such as high-harmonic generation (HHG) and multiphoton
                      microscopy (MPM)—of anultrafast fiber laser system: energy
                      scaling capability and wavelength tunability. High
                      photon-flux extreme ultraviolet sources enabled by HHG
                      desire high power (>100 W), high repetition-rate (>1 MHz)
                      ultrafast driving laser sources. We have constructed from
                      scratch a high-power Yb-fiber laser system using the
                      well-known chirped-pulse amplification (CPA) technique. Such
                      a CPA system capable of producing ∼200-W average power
                      consists of a monolithic Yb-fiber oscillator, an all-fiber
                      stretcher, a pre-amplifier chain, a main amplifier
                      constructed from rode-type large pitch fiber, and a
                      diffraction-grating based compressor. To increase the HHG
                      efficiency, ultrafast pulses with duration <60 fs are highly
                      desired. We proposed and demonstrated a novel amplification
                      technique, named as pre-chirp managed amplification (PCMA).
                      We successfully constructed an Yb-fiber based PCMA system
                      that outputs 75-MHz spectrally broadened pulses with >130-W
                      average power. The amplified pulses are compressed to 60-fs
                      pulses with 100-W average power, constituting a suitable HHG
                      driving source. MPM is a powerful biomedical imaging tool,
                      featuring larger penetration depth while providing the
                      capability of optical sectioning. Although femtosecond
                      solid-state lasers have been widely accepted as the standard
                      option as MPM driving sources, fiber-based sources have
                      received growing research efforts due to their superior
                      performance. In the second part of this thesis, we both
                      theoretically and experimentally demonstrated a new method
                      of producing wavelength widely tunable femtosecond pulses
                      for driving MPM. We employed self-phase modulation to
                      broaden a narrowband spectrum followed by bandpass filters
                      to select the rightmost/leftmost spectral lobes. Widely
                      tunable in 820-1225 nm, the resulting sources generated
                      nearly transform-limited, ∼100 fs pulses. Using short
                      fibers with large mode-field-diameter for spectral
                      broadening, we obtained ultrashort pulses with the pulse
                      energies up to 20 nJ. We applied such an enabling source to
                      drive MPM imaging of both cancer cells and skin samples.},
      cin          = {CFEL-UFOX / FS-CFEL-2 / CFEL-ULOCM},
      cid          = {I:(DE-H253)CFEL-UFOX-20160927 /
                      I:(DE-H253)FS-CFEL-2-20120731 /
                      I:(DE-H253)CFEL-ULOCM-20160928},
      pnm          = {6211 - Extreme States of Matter: From Cold Ions to Hot
                      Plasmas (POF3-621) / VH-NG-804 - Towards Laboratory-Based
                      Ultrafast Bright EUV and X-ray Sources
                      $(2015_IVF-VH-NG-804)$},
      pid          = {G:(DE-HGF)POF3-6211 / $G:(DE-HGF)2015_IVF-VH-NG-804$},
      experiment   = {EXP:(DE-H253)CFEL-Exp-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2017-00199},
      url          = {https://bib-pubdb1.desy.de/record/316801},
}