新型抗弯曲大模场面积光子晶体光纤

研制出一种新型抗弯曲大模场面积石英光子晶体光纤. 利用光子晶体光纤结构设计的灵活性, 通过规划缺陷的位置及空气孔的尺寸, 实现了大模场面积单模及低弯曲损耗特性.应用建立的实际光子晶体光纤特性分析模型, 研究了研制光纤的模式特性和弯曲特性, 在波长1064 nm处, 平直状态下光纤的模场面积可以达到2812 μm², 基模限制损耗为0.00024 dB/m, 高阶模限制损耗高于1.248 dB/m. 基模和高阶模之间的高传输损耗差, 保证了在获得大模场面积的同时实现单模传输. 弯曲半径和弯曲方向角所带来弯曲损耗变化的研究结果显示, 即使在弯曲半径小到5 cm时, 弯曲损耗也在10^-3 dB/m量级以下, 而且在弯曲半径为30 cm时光纤可承受的弯曲方向角范围扩展至-60°–60°. 研制的光纤具有良好的低弯曲损耗特性, 可有效解决非对称结构所带来的光纤弯曲特性对弯曲方向角敏感的问题. 该光纤在高功率光纤激光器、放大器及高功率传输等技术领域具有重要的应用价值. 关键词： 光子晶体光纤 大模场面积 低弯曲损耗 弯曲方向角

A novel bend-resistant large-mode-area photonic crystal fiber

A novel bend-resistant large-mode-area silica photonic crystal fiber (PCF) is proposed and fabricated. With the advantage of flexible design on the PCF configuration, the properties of large-mode-area, single mode propagation and low bend loss can be simultaneously achieved by intentionally designing the position of defect and the size of air holes. Modal properties and bending loss of the actual PCF can be evaluated with previous model for assessing the properties of the actual fiber. Numerical results demonstrate that this fiber has an extremely large mode area of 2812 μm², low confine loss of 0.00024 dB/m of the fundamental mode and high confine loss of over 1.248 dB/m of higher order mode at a wavelength of 1064 nm when the optical fibre is kept straight. The large difference in propagation loss levels between fundamental mode and higher order modes ensures the efficient single-mode propagation in the fiber core. Furthermore, the effects of bend radius and bend direction angle on bend loss are investigated when the fiber is bent. Even if bend radius is as small as 5 cm, bend loss of this fiber is still below 10^-3 dB/m. It is found that the proposed fiber has the negligible bending loss at a bending radius of 30 cm with the bending angle ranging from -60° to 60°. These results illustrate that the fabricated fiber possesses the better bend resistant properties and can overcome the sensitivity to bend direction angle caused by the asymmetric structure. The fabricated fiber will play an important role in developing high power fiber laser, fiber amplifier and high power delivery application.