Experimental measurement of group velocity dispersion during operation in cladding-pumped large-mode-area Yb-doped fibers

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Contributors

  • Tobias Baselt - , University of Applied Sciences Zwickau (Author)
  • Christopher Taudt - , University of Applied Sciences Zwickau (Author)
  • Andres Fabian Lasagni - , Chair of Laser-based Manufacturing, Fraunhofer Institute for Material and Beam Technology (Author)
  • Peter Hartmann - , University of Applied Sciences Zwickau, Fraunhofer Institute for Material and Beam Technology (Author)

Abstract

Ever higher output power of fiber lasers leads to growing requirements on the fibers used. The increasing intensity of light in the fiber core is compensated by enlargement of the area of the doped core. The guiding properties of the optical fiber are significantly affected and must be very accurately defined. This high intensity leads to significant deviations of the guiding properties of the optical fiber during laser operation due to absorption and thermal effects. In particular, information about the change in group-velocity dispersion(GVD) during operation is important for the development of high power fiber laser systems. In an effort to gather such knowledge, this paper presents the results of dispersion characterization measurements using ytterbium-doped large-mode-area double-clad fibers which are cladding pumped at a wavelength of 975 nm. The direct measurement of the GVD in the emission range of the ytterbium-doped fibers (1000 nm to 1150 nm) is shown. GVD characteristics of two different large-mode-area double-clad fibers with defined launching pump laser power level were systematically analyzed. The dispersion parameters for different fiber designs and various doping levels are investigated over a broad spectral range in the emission area of Yb-doped fiber samples for controlled sets of operating parameters. The experiment utilizes a supercontinuum source developed within this laboratory as well as a Mach-Zehnder interferometer with a dual-channel spectral-detection system sensitive to wavelengths from 0.95 μm to 1.75 μm. Temporally resolved spectrograms recorded at distinct delay positions enable the detection of interference fringes for the equalization wavelength. By applying a Sellmeier polynomial fit to the wavelength dependent differential group-delay function, the GVD can be derived. The measured Yb-doped large-mode-area fibers show a variation of the doping concentration between 0.7 mass percent to 3 mass percent of ytterbium. The measurement of the Yb-doped large-mode-area fiber with or without optical load on the sample during the measurement was examined.

Details

Original languageEnglish
Title of host publicationOptical Measurement Systems for Industrial Inspection IX
EditorsArmando Albertazzi G., Peter Lehmann, Wolfgang Osten
PublisherSPIE - The international society for optics and photonics
ISBN (electronic)9781628416855
Publication statusPublished - 2015
Peer-reviewedYes

Publication series

SeriesProceedings of SPIE - The International Society for Optical Engineering
Volume9525
ISSN0277-786X

Conference

TitleOptical Measurement Systems for Industrial Inspection IX
Duration22 - 25 June 2015
CityMunich
CountryGermany

External IDs

ORCID /0000-0003-4333-4636/work/196675572

Keywords

Keywords

  • group velocity dispersion during operation, large effective mode area (LMA) fibers, multicore fibers, Time-frequency-domain dispersion measurement