Alyshev Sergey, Vakhrushev Alexander, Umnikov Andrey, Velmiskin Vladimir, Oleinik Denis, Melkumov Mikhail, Semjonov Sergey, Riumkin Konstantin, Khegai Aleksandr, Firstova Elena, Iskhakova Lyudmila, Firstov Sergei
Opt Express. 2024 Aug 12;32(17):29214-29226. doi: 10.1364/OE.531655.
Multicore fibers are promising structures with specific light propagation properties, which can be managed to benefit several applications in optical communications, fiber lasers and amplifiers, high-resolution imaging, and fiber-based sensors. The current use of multicore fibers in laser technology is mainly focused on in-phase coherent beam combining in far-field regions (out-cavity) using bulk optical elements. However, this approach is challenging in terms of the power scalability of all-fiber lasers (intra-cavity), particularly with using low-gain media, where it is needed to provide mode-coupling (supermode propagation) stability along relatively long lengths. Here, we report a conceptual design and fabrication of a multicore bismuth-doped fiber that is capable of achieving light amplification and stable lasing in the E-telecom band inside the cavity using the supermode selection approach. By analysis of experimental and simulation data, it was found that the employment of the proposed design of a Bi-doped fiber provides a considerable advantage over the single-core fiber in terms of laser performance (output power, slope efficiency) in the cladding-pumped configuration. These results open up new opportunities for further advancement of the optical fiber technology towards efficient bismuth-doped fiber-integrated amplifiers and lasers for the O+E+S+C+L+U-telecom bands, which may find important applications, especially for the development of next-generation multiband optical transmission systems.
多芯光纤是具有特定光传播特性的有前景的结构，可加以利用以有益于光通信、光纤激光器和放大器、高分辨率成像以及基于光纤的传感器等多种应用。目前多芯光纤在激光技术中的应用主要集中在使用块状光学元件在远场区域（腔外）进行同相相干光束合成。然而，这种方法对于全光纤激光器（腔内）的功率可扩展性具有挑战性，特别是在使用低增益介质时，需要在相对较长的长度上提供模式耦合（超模式传播）稳定性。在此，我们报告了一种多芯铋掺杂光纤的概念设计和制造，该光纤能够使用超模式选择方法在腔内实现电信E波段的光放大和稳定激光发射。通过对实验和模拟数据的分析发现，在包层泵浦配置下，所提出的铋掺杂光纤设计在激光性能（输出功率、斜率效率）方面比单芯光纤具有相当大的优势。这些结果为光纤技术进一步向用于O+E+S+C+L+U电信波段的高效铋掺杂光纤集成放大器和激光器发展开辟了新机会，这可能会有重要应用，特别是对于下一代多波段光传输系统的开发。
