5 W 120 fs pulses directly from a 1.2 GHz single-mode Er-doped fiber

We introduce a single-mode Erbium-doped master oscillator power amplifier (MOPA) fiber laser, capable of directly generating 100 fs pulses at 2.2 W and 120 fs pulses at 4.5 W of average power. This laser operates at a pulse repetition rate of 1.2 GHz with a repetition rate multiplier, at the central wavelength around 1550 nm. The laser system comprises a passively mode-locked oscillator with a repetition rate of 77.6 MHz and an average power of 16.3 mW followed by a repetition rate multiplier and a cladding-pumped co-doped Er-Yb fiber laser. 100 fs long pulses, as the shortest pulse duration, was directly achieved at an output power of 2.2 W. In this experiment, the pulse dynamic at different output powers has been studied and verified by simulation. This developed system is employed in micromachining and sub-surface silicon processing at low pulse energy at a GHz-range repetition rate.