Near-complete stored energy extraction from fiber amplifiers in ultrashort >10mJ energy pulses using coherent pulse stacking amplification (Conference Presentation)

10mJ energy extraction from a single Yb-doped 85µm core CCC fiber has been achieved using coherent pulse stacking amplification (CPSA) technique. This has been achieved by amplifying a burst of 81 stretched pulses with modulated amplitudes and phases, in a Yb-doped fiber CPA system where it is amplified to 10mJ with low nonlinearity, and coherently stacked into a single pulse with 4+4 cascading GTI cavities. The burst is generated by sending femtosecond pulses from a 1GHz repetition rate mode-locked fiber oscillator into a pair of amplitude and phase electro-optic modulators, where the burst is carved out and pre-shaped to compensate for strong saturation effect in fiber CPA system and to provide correct relative phases for coherent pulse stacking. After each pulse is stretched to approximately 1-ns, the burst is amplified through several cascading fiber amplifiers and down-counted to 1kHz repetition rate, and it extracts >90% stored energy from the last Yb-doped 85µm core CCC fiber. This multi-mJ burst of 81 pulses is then coherently stacked into a single pulse in 4+4 multiplexed GTI cavities consisting of 4 sets of 1ns-roundtrip cavities followed by 4 sets of 9-ns roundtrip cavities. After stacking, the stretched pulse is compressed to <540fs using diffraction-grating pulse compressor. CPSA enables generation of multi-mJ femtosecond pulses with one fiber amplifier channel.