title: Single-mode large-mode-area laser fiber with ultralow numerical aperture and high beam quality.
abstract: By using the chelate precursor doping technique, we report on an ytterbium-doped aluminophosphosilicate (APS) large-mode-area fiber with ultralow numerical aperture of 0.036 and effective fundamental mode area of ∼550  μm2. With a bend diameter of 600 mm, the bending loss of fundamental mode LP01was measured to be <10-3dB/m, in agreement with the corresponding simulation results, while that of higher order mode LP11is >100  dB/m at 1080 nm. Measured in an all-fiber oscillator laser cavity, 592 W single-mode laser output was obtained at 1079.64 nm with high-beam quality M2of 1.12. The results indicate that the chelate precursor doping technique is a competitive method for ultralow numerical aperture fiber fabrication, which is very suitable for developing single-mode seed lasers for high power laser systems.
authors.forename: Kun
authors.initials: K
authors.lastname: Peng
authors.forename: Huan
authors.initials: H
authors.lastname: Zhan
authors.forename: Li
authors.initials: L
authors.lastname: Ni
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Wang
authors.forename: Yuying
authors.initials: Y
authors.lastname: Wang
authors.forename: Cong
authors.initials: C
authors.lastname: Gao
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Li
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Jing
authors.forename: Aoxiang
authors.initials: A
authors.lastname: Lin