1.6  kW Yb fiber amplifier using chirped seed amplification for stimulated Brillouin scattering suppression.
In a high power fiber amplifier, a frequency-chirped seed interrupts the coherent interaction between the laser and Stokes waves, raising the threshold for stimulated Brillouin scattering (SBS). Moving the external mirror of a vertical cavity surface-emitting diode laser 0.2 μm in 10 μs can yield a frequency chirp of 5×1017Hz/s at a nearly constant output power. Opto-electronic feedback loops can linearize the chirp, and stabilize the output power. The linear variation of phase with time allows multiple amplifiers to be coherently combined using a frequency shifter to compensate for static and dynamic path length differences. The seed bandwidth, as seen by the counter-propagating SBS, also increases linearly with fiber length, resulting in a nearly-length-independent SBS threshold. Experimental results at the 1.6 kW level with a 19 m delivery fiber are presented. A numerical simulation is also presented.
Jeffrey O
JO
White
Mark
M
Harfouche
John
J
Edgecumbe
Naresh
N
Satyan
George
G
Rakuljic
Vijay
V
Jayaraman
Christopher
C
Burgner
Amnon
A
Yariv