Recently, the research team led by Professors Lili Hu and Chunlei Yu from the Special Glass and Fiber R&D Center at the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, has made a significant breakthrough in the design and fabrication of novel Nd-doped silica fibers and their application in high-power narrow-linewidth single-frequency fiber laser (SFFL) at ~900 nm.

High-power narrow-linewidth Nd-doped SFFLs operating at ~900 nm hold important application prospects in the generation of blue/ultraviolet single-frequency lasers, underwater communication and water-vapor absorption lidar, and have thus attracted considerable attention in recent years. However, due to the constraints of 1.06 μm four-level gain competition and three-level reabsorption effects, the reported output power of ~900 nm SFFLs has long been limited to below 10 W. It is a great challenge to construct high-power all-fiber SFFLs at this band.

To address these bottlenecks, the research team innovatively proposed a direct coordination engineering approach to enhance fluorescence at ~900 nm, and successfully developed a series of novel Nd-doped silica fibers for all-fiber MOPA system applications:

1) 4/125 μm highly Nd-doped single-mode fiber for DBR single-frequency seed (representative publications: Chinese Journal of Lasers, 2023, DOI: 10.3788/CJL230664; Advanced Photonics Nexus, 2023, DOI: 10.1117/1.apn.2.6.066002; Optics Express, 2023, DOI: 10.1364/OE.479435);

2) Polarization-maintaining (PM) 10/125 μm Nd-doped silica fiber for pre-amplification stages (representative publications: Photonics Research, 2026, DOI: 10.1364/PRJ.600265; High Power Laser Science and Engineering, 2026, DOI: 10.1017/hpl.2026.10116);

3) PM 20/125 μm large-mode-area Nd-doped silica fiber for main amplification stages (representative publications: Chinese Journal of Lasers, 2025, DOI: 10.3788/CJL251143; Chinese Journal of Lasers, 2026, DOI: 10.3788/CJL251640; Optics Letters, 2026, DOI: 10.1364/OL.604063).

Based on these homemade fibers, as shown in Figure 1, the team constructed an all-fiber amplification system and demonstrated a 103 W SFFL output at 922 nm with kilohertz linewidth for the first time. As shown in Figure 2, such power level represents an improvement of one order of magnitude over the previously reported highest single-frequency output power.

Figure 1. 100 W-class 922 nm SFFLs based on homemade Nd-doped silica fibers.

Figure 2. The typical progress of Nd-doped SFFLs at ~900 nm.

The above series of work was supported by the National Natural Science Foundation of China, the Shanghai Natural Science Foundation, and the Strategic Priority Research Program of the Chinese Academy of Sciences