kW Level Narrow Linewidth Yb Fiber Amplifiers for Beam Combining

摘要

Beam combining of fiber lasers has attracted much interest as a practical means to power scale fiber laser/amplifiers beyond the limitations of a single mode output from an individual fiber [1]. Almost all of the high power demonstrations to date that deliver good beam quality after the combing process (coherent and spectral) require some linewidth control for efficient combining, typically less than 10GHz [2,3,4]. Previously we demonstrated single mode, Yb-doped LMA fiber amplifiers operated with around 7GHz linewidth at 1kW output power [5]. In this paper, the latest generations of these amplifiers, based on the latest developments in LMA Yb-doped fiber technology demonstrate the capability to operate with linewidths around 3GHz at the 1kW power level. We present the latest data on optical properties of these new Yb-doped amplifiers and the SBS threshold as a function of input seed laser linewidth and discuss the technologies being developed to operate at higher power levels and narrower linewidths.