title: High-energy and high-peak-power nanosecond pulse generation with beam quality control in 200-microm core highly multimode Yb-doped fiber amplifiers.
abstract: We explored high-energy and high-peak-power pulse generation in large-core multimode fiber amplifiers, achieving what is to our knowledge the highest reported energies, up to 82 mJ for 500-ns pulses, 27 mJ for 50-ns pulses, and 2.4-MW peak power for 4-ns pulses at 1064 nm, using 200-microm-diameter and 0.062-N.A. core Yb-doped double-clad fiber amplifiers. The highly multimode nature of the fiber core was mitigated by use of a coiling-induced mode-filtering effect to yield a significant improvement in output-beam quality from M2 = 25 from an uncoiled fiber to M2 = 6.5 from a properly coiled fiber, with the corresponding reduction in number of propagating transverse modes from > or = 200 to < or = 20.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109-2122, USA. myc@umich.edu
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: Cheng
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chang
authors.forename: Almantas
authors.initials: A
authors.lastname: Galvanauskas
authors.forename: Pri
authors.initials: P
authors.lastname: Mamidipudi
authors.forename: Rupak
authors.initials: R
authors.lastname: Changkakoti
authors.forename: Peter
authors.initials: P
authors.lastname: Gatchell