Compact high-power GHz intra-burst repetition rate all-in-fiber CPA system with LMA fiber power amplifier

A compact high-power femtosecond (similar to 640 fs) GHz intra-burst repetition rate all-in-fiber CPA system operating at 3.26 GHz intra-burst and 200 kHz burst repetition rate regime with two configurations of large mode area (LMA and PCF) cladding-pumped Yb-doped fiber power amplifiers were presented in this work. Significantly high average power levels of 6 W (LMA fiber power amplifier) and >20 W (PCF power amplifier) were achieved which corresponded to a maximum energy of 30 mu J and >100 mu J per burst respectively. Two burst shaping layouts were introduced in this experimental setup obtaining desired burst shape using one or two acousto-optic modulators, pulse repetition rate multiplier based on a cascaded 2x2 fiber coupler sequence with a splitting ratio of 50/50 and controlled using arbitrary waveform generator. High power all-in-fiber CPA system with LMA fiber power amplifier operating at GHz burst regime was compared to the system operating at MHz pulse repetition rate regime which allowed to achieve 1.5 mu J energy pulses of good pulse quality at the output of the laser system at a repetition rate of 4 MHz.