Thermal-lens effect on transverse modes in the confined-gain Yb-doped fiber

• Published in: Optical fiber technology 2024-05, Vol.84, p.103715, Article 103715
• Main Authors: Liu, Pengfei, Cao, Jianqiu, Liu, Wenguang, Chen, Jinbao
• Format: Article
• Language: English
• Subjects: Confined-gain Yb-doped fiber; Gain competition; Thermal-lens effect
• ISSN: 1068-5200; 1095-9912
• DOI: 10.1016/j.yofte.2024.103715

In this paper we studied thermal-lens effect on transverse modes in the confined-gain Yb-doped fiber for the first time, to the best of our knowledge. It is found that the thermal-lens effect is enhanced with the reduction of doped area due to the higher thermal density in the doped area. Then, the variations of three low-order transverse modes (i.e., fundamental, LP11 and LP02 modes) with the heat load and doped diameter are studied, and the mode areas and overlapping factors with the doped area of these transverse modes are also discussed. The gain competition of these transverse modes is also investigated by calculating the differential-gain ratio with the purpose of achieving the single-mode operating. It is found that the stronger thermal-lens effect will result in the reduction of optimum doped diameter for suppressing high-order modes. This study can provide significant guidance for designing the confined-gain Yb-doped fibers for the applications in high-power fiber lasers and amplifiers.