Mid-infrared (MIR) fiber lasers are important for a wide range of applications in sensing, spectroscopy, imaging, defense, and security. Some progress has been made in the research of MIR fiber lasers based on soft glass fibers, however, the emission range of rare-earth ions and the robustness of the host materials are still a major challenge for MIR fiber lasers. The large number of gases provide a variety of optical transitions in the MIR band. When combined with recent advances in low-loss hollow-core fiber (HCF), there is a great opportunity for gas-filled fiber lasers to further extend the radiation to the MIR region. Here, a 4.8-μm CO-filled silica-based HCF laser is reported for the first time. This is enabled by an in-house manufactured broadband low-loss HCF with a measured loss of 1.81 dB/m at 4.8 μm. A maximum MIR output power of 46 mW and a tuning range of 180 nm (from 4644 to 4824 nm) are obtained by using an advanced 2.33-μm narrow-linewidth fiber laser. This demonstration represents the longest-wavelength silica-based fiber laser to date, while the absorption loss of bulk silica at 4824 nm is up to 13, 000 dB/m. Further wavelength expansion could be achieved by changing the pump absorption line and optimizing the laser structure.

中红外 （MIR） 光纤激光器对于传感、光谱学、成像、国防和安全领域的广泛应用非常重要。基于软玻璃纤维的 MIR 光纤激光器的研究取得了一些进展，但稀土离子的发射范围和主体材料的稳健性仍然是 MIR 光纤激光器面临的主要挑战。大量的气体在 MIR 波段提供了各种光跃迁。当与低损耗空芯光纤 （HCF） 的最新进展相结合时，充气光纤激光器有很大的机会将辐射进一步扩展到 MIR 区域。在这里，首次报道了 4.8 μm CO 填充二氧化硅基 HCF 激光器。这是通过内部制造的宽带低损耗 HCF 实现的，在 4.8 μm 处测得的损耗为 1.81 dB/m。通过使用先进的 2.33 μm 窄线宽光纤激光器，最大 MIR 输出功率为 46 mW，调谐范围为 180 nm（从 4644 到 4824 nm）。该演示代表了迄今为止波长最长的二氧化硅基光纤激光器，而块状二氧化硅在 4824 nm 处的吸收损失高达 13， 000 dB/m。通过改变泵浦吸收线和优化激光器结构，可以实现进一步的波长扩展。