title: Active phase and polarization locking of a 1.4 kW fiber amplifier.
abstract: A three-stage Yb-fiber amplifier emitted 1.43 kW of single-mode power when seeded with a 25 GHz linewidth master oscillator (MO). The amplified output was polarization stabilized and phase locked using active heterodyne phase control. A low-power sample of the output beam was coherently combined to a second fiber amplifier with 90% visibility. The measured combining efficiency agreed with estimated decoherence effects from fiber nonlinearity, linewidth, and phase-locking accuracy. This is the highest-power fiber laser that has been coherently locked using any method that allows brightness scaling.
authors.affiliation: Northrop Grumman Aerospace Systems, One Space Park, R1-1184D, Redondo Beach, California 90278, USA*Corresponding author: gregory.goodno@ngc.com
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Goodno
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: McNaught
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Rothenberg
authors.forename: Timothy S
authors.initials: TS
authors.lastname: McComb
authors.forename: Peter A
authors.initials: PA
authors.lastname: Thielen
authors.forename: Michael G
authors.initials: MG
authors.lastname: Wickham
authors.forename: Mark E
authors.initials: ME
authors.lastname: Weber