高功率光纤激光热光效应及模式不稳定阈值特性研究  

Thermo-Optic Effect and Mode Instability Threshold Characteristics of High-Power Fiber Laser

作　　者：李学文 于春雷 沈辉[1] 柏刚[1,2] 邹星星 尤阳 全昭 李秋瑞[1] 漆云凤[1,2] 何兵[1,2] 周军 Li Xuewen;Yu Chunlei;Shen Hui;Bai Gang;Zou Xingxing;You Yang;Quan Zhao;Li Qiurui;Qi Yunfeng;He Bing;Zhou Jun(Shanghai Key Laboratory of All Solid-State Laser and Applied Techniques,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院上海光学精密机械研究所上海市全固态激光器与应用技术重点实验室,上海201800 [2]中国科学院大学材料与光电研究中心,北京100049

出　　处：《中国激光》2019年第10期21-29,共9页Chinese Journal of Lasers

基　　金：国家自然科学基金(61735007,61405202,61705243);上海市自然科学基金(16ZR1440100,16ZR1440200);上海市优秀技术带头人计划(17XD1424800);上海市青年科技英才杨帆计划(17YF1421200)

摘　　要：针对高功率强抽运条件下,热光效应及其引起的模式不稳定效应对高功率大模场光纤功率及亮度提升的限制,理论仿真了有源光纤吸收系数变化对光纤热沉积、热致折射率以及光纤数值孔径的影响,分析表明高吸收系数光纤带来更高热负荷密度,在热光效应调制下加剧光纤数值孔径的增大程度,从而降低光纤激光的模式不稳定阈值。在理论研究基础上设计并制备了两款不同抽运吸收系数光纤样品并展开了高功率模式不稳定实验研究。实验结果证明,吸收系数为1.71dB/m的光纤样品的模式不稳定阈值激光功率约为800W,吸收系数为1.20dB/m的光纤样品在输出激光功率达到1700W时仍未观测到任何模式的不稳定现象,实验结果验证了降低光纤的抽运吸收系数可提升热致模式不稳定阈值的理论分析。该研究结果为设计研制大模场有源光纤,并获得更高功率光纤激光输出提供了一种新颖有效的技术途径。To study the limits of improvements of the high-power large-field fiber power and brightness caused by the thermo-optic effect and thermal-induced mode instability under strong pumping conditions,we analyze the influence of the variation of absorption coefficient on the thermal deposition,thermal-induced refractive index,and numerical aperture of a fiber.Results show that a fiber with high absorption coefficient causes a high heat load density,and its numerical aperture increases under the thermal-optic effect modulation,thereby reducing the mode instability threshold.Based on the theoretical research,fibers with two different pump absorption coefficients are designed and fabricated,and high-power mode instability experiments are performed.Experimental results show that the mode instability threshold power is 800Wfor the high pump absorption fiber with an absorption coefficient of 1.71dB/m.However,for the fiber with a low pump absorption coefficient of 1.20dB/m,the mode instability is not observed when the output power reaches 1700 W.Thus,the mode instability threshold can be considerably improved by decreasing the pump absorption coefficient of the active fiber.These results are significant to the development of high-power active optical fibers and provide a novel and effective technical approach for obtaining high-power fiber laser output.

关 键 词：光纤激光器 增益光纤 模式不稳定 抽运吸收系数 热光效应 

分 类 号：TN248[电子电信—物理电子学]