Amplifying nanosecond optical pulses at 1053 nm with an all-fiber regenerative amplifier

Nanosecond, 1053 nm optical pulses are amplified from 15 pJ to 240 nJ by a Yb-doped all-fiber regenerative amplifier (AFRA), achieving an overall gain of 42 dB. To the best of our knowledge, this is the highest output-pulse energy from an AFRA ever reported. Techniques for suppressing amplified spontaneous emission are employed to favor the signal gain 23 nm off the gain peak of the Yb-doped fiber. Numerical simulations show that increasing the number of round trips and operating the AFRA at saturation will increase the output level and improve the output stability. This is currently limited by the onset of bifurcation instability, which can be avoided at low repetition rates.