Narrow-bandwidth actively Q-switched all-fiber laser by suppressing ASE gain self-saturation

This paper proposes and demonstrates a novel method to produce the narrow-bandwidth, narrow-pulse-width and high-repetition-rate pulses with actively Q-switched ring-cavity all-fiber lasers. By using a specially designed low-reflectivity cladding power stripper in the cavity, and inserting a length-optimized ytterbium-doped single-cladding fiber self-pumped by the backward amplified spontaneous emission (ASE) from the YDF to improve the amplification of the initial weak ASE feedback by the narrowband filter, the ASE gain self-saturation can be suppressed efficiently, and the lasing pulses can be established quickly within the opening time of Q-switch even operating for very high repetition-rate. With the proposed technique, watt-level Q-switched pulses with bandwidth and pulse width narrowed to 0.15 nm and 9 ns, and repetition rate up to 175 kHz are achieved.