Towards MW-level All-Glass Ytterbium Tapered Double-Clad Fiber Laser

This paper presents all-fiber master oscillator-power amplifier systems that deliver high average power picosecond pulses with durations of 6 to 50ps, a tunable repetition rate within 360 kHz to 1 GHz range, and peak powers of up to 2 MW. The experimental investigations incorporate two Yb-doped spun tapered double-clad fibers gain modules with 60 μm and 92 μm core diameters. Utilizing the 92 μm core module picosecond pulses with high average power of 625 W average power at 20 MHz, and 645 W at 1 GHz were achieved. The gain module with 60 μm core diameter enabled to deliver a high peak power pulsed-signal with 2 MW peak power at 360 kHz and 50 ps pulse duration, while 26 MHz and 6 ps pulses reached 1 MW peak power. In all configurations, near-diffraction-limited beam quality, M² < 1.4, was maintained without any traces of transverse mode instability (TMI). These compact, TMI-free, high-power amplifiers offer a promising platform for high-power ultrafast fiber lasers for the vast majority of industrial applications.