Nanosecond-pulsed fiber lasers are widely used in laser processing, remote sensing, and communications, but their performances are often limited by nonlinear effects such as four-wave mixing (FWM), which causes unstable sub-peaks and restricts further power scaling.
A research team led by Prof. ZHAO Wei from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of Chinese Academy of Sciences has developed a novel method to significantly enhance the performance of high-energy, narrow-linewidth, nanosecond-pulsed fiber lasers by leveraging stimulated Brillouin scattering (SBS) for pulse shaping.Their findings were published in Optics and Lasers in Engineering.
By introducing a segment of polarization-maintaining large-mode-area germanium-doped fiber into the pre-amplifier stage, the team successfully induced SBS to reshape the temporal profile of the injected pulse, effectively suppressing unwanted sub-peaks and increasing the nonlinear threshold of the main amplifier.
The experimental results demonstrated that the SBS-induced pulse shaping method increased the output power of the main amplifier from 3.4 W to 5.8 W, with pulse energy rising from 0.34 mJ to 0.58 mJ, while maintaining a narrow linewidth of 0.082 nm, a pulse width of 4 ns, a repetition rate of 10 kHz, and near-diffraction-limited beam quality (M2 < 1.2). The output also exhibited excellent power stability with less than 1.5% RMS fluctuation over 10 minutes.
Unlike conventional electro-optic or acousto-optic pulse shaping techniques, which are limited to hundreds of nanoseconds and low power levels, the SBS-based method operates during the amplification process and is capable of shaping pulses at the 10 ns scale. This approach not only improves the pulse profile but also enhances the overall energy extraction efficiency by broadening the spectral sidebands and reducing peak power density, thereby mitigating FWM and other nonlinear effects.
This study provides a new strategy for overcoming power limitations in narrow-linewidth pulsed fiber amplifiers and highlights the positive role of SBS in laser amplification systems. And it is expected to benefit applications requiring high-energy, high-quality nanosecond pulses, such as lidar, precision manufacturing, and nonlinear frequency conversion.
(Available online 3 September 2025)
Fig. Sketch of high-energy nanosecond pulsed fiber laser. (Image by XIOPM)
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