Numerical study of a bi-directional in-band pumped dysprosium-doped fluoride fiber laser at 3.2 µm

Abstract

Dy³⁺-doped fluoride fiber lasers have important applications in environment monitoring, real-time sensing, and polymer processing. At present, achieving a high-efficiency and high-power Dy³⁺-doped fluoride fiber laser in the mid-infrared (mid-IR) region over 3 µm is a scientific and technological frontier. Typically, Dy³⁺-doped fluoride fiber lasers use a unidirectional pumping method, which suffers from the drawback of high thermal loading density on the fiber tips, thus limiting power scalability. In this study, a bi-directional in-band pumping scheme, to address the limitations of output power scaling and to enhance the efficiency of the Dy³⁺-doped fluoride fiber laser at 3.2 µm, is investigated numerically based on rate equations and propagation equations. Detailed simulation results reveal that the optical–optical efficiency of the bi-directional in-band pumped Dy³⁺-doped fluoride fiber laser can reach 75.1%, approaching the Stokes limit of 87.3%. The potential for further improvement of the efficiency of the Dy³⁺-doped fluoride fiber laser is also discussed. The bi-directional pumping scheme offers the intrinsic advantage of mitigating the thermal load on the fiber tips, unlike unidirectional pumping, in addition to its high efficiency. As a result, it is expected to significantly scale the power output of Dy³⁺-doped fluoride fiber lasers in the mid-IR regime.

摘要

掺镝氟化物光纤激光器在环境监测、实时传感和聚合物加工等方面具有重要应用。目前, 在>3 µm的中红外区域获得高效率、高功率的掺镝氟化物光纤激光是科技前沿领域。通常, 掺镝氟化物光纤激光器采用单向泵浦方案, 但其存在光纤端面高热负载密度的缺点, 限制了功率的提升。本研究基于速率方程和传输方程, 数值研究了一种双向同带泵浦方案, 旨在解决3.2 µm掺镝氟化物光纤激光器输出功率提升的限制, 并提升其效率。仿真结果表明, 双向同带泵浦的掺镝氟化物光纤激光器的光光效率可达75.1%, 接近斯托克斯极限87.3%。同时, 讨论了进一步提高掺镝氟化物光纤激光器效率的潜力。与单向泵浦相比, 双向泵浦方案除了高效率外, 还具有减轻光纤端面热负荷的固有优势。因此, 该方案有望显著提高掺镝氟化光纤激光器在中红外波段的输出功率。