title: 400-W near diffraction-limited single-frequency all-solid photonic bandgap fiber amplifier.
abstract: An ytterbium-doped large-mode area photonic bandgap fiber is used to demonstrate 400 W of single-frequency output at 1064 nm with excellent beam quality and minimal stimulated Brillouin scattering. The fiber possesses all-solid microstructures embedded in the cladding and a core composed of phosphosilicate with a diameter of ∼50  μm. As the signal power is pushed beyond 450 W, there is degradation in the beam quality due to the modal instability. We briefly discuss techniques to alleviate this problem in future designs. To the best of our knowledge, the 400-W single-frequency near diffraction-limited output far exceeds the current state-of-the-art from such type of fiber amplifier.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pulford
authors.forename: Thomas
authors.initials: T
authors.lastname: Ehrenreich
authors.forename: Roger
authors.initials: R
authors.lastname: Holten
authors.forename: Fanting
authors.initials: F
authors.lastname: Kong
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Hawkins
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
authors.forename: Iyad
authors.initials: I
authors.lastname: Dajani