title: Optimizing mode instability in low-NA fibers by passive strategies.
abstract: Systematic experimental investigations toward the mode instability (MI) threshold in low-NA fibers are performed. By testing several fibers with varying V-parameters drawn from the same preform, a high degree of reproducibility of the experimental conditions could be achieved. This allows for systematic investigations on isolated parameters influencing the complex behavior of MI. A maximum MI threshold of 2 kW could be demonstrated for the tested fibers, which represents a new record output power for narrow linewidth fiber amplifiers. The MI threshold was found to sensitively depend on the V-parameter for large V-parameters (>2), but to be robust for smaller V-parameters. Furthermore, the fiber bending diameter and the seed excitation conditions were identified to sensitively influence the MI threshold.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Haarlammert
authors.forename: Bettina
authors.initials: B
authors.lastname: Sattler
authors.forename: Andreas
authors.initials: A
authors.lastname: Liem
authors.forename: Maximilian
authors.initials: M
authors.lastname: Strecker
authors.forename: Johannes
authors.initials: J
authors.lastname: Nold
authors.forename: Thomas
authors.initials: T
authors.lastname: Schreiber
authors.forename: Ramona
authors.initials: R
authors.lastname: Eberhardt
authors.forename: Andreas
authors.initials: A
authors.lastname: Tünnermann
authors.forename: Klaus
authors.initials: K
authors.lastname: Ludewigt
authors.forename: Markus
authors.initials: M
authors.lastname: Jung