空间激光与单模光纤和光子晶体光纤的耦合效率  

Coupling efficiency of free-space laser coupling into single mode fiber and photonic crystal fiber

作　　者：陈雪坤[1,2] 张璐[1,2] 吴志勇[1] 

机构地区：[1]中国科学院长春光学精密机械与物理研究所,吉林长春130033 [2]中国科学院大学,北京100049

出　　处：《中国光学》2013年第2期208-215,共8页Chinese Optics

基　　金：中科院长春光机所所内创新资助项目(No.Y10532B110)

摘　　要：为了设计最优光纤耦合系统,利用高斯模场近似单模阶跃光纤的模场和大模面积光子晶体光纤的模场,推导出了理想情况下空间激光与这两种光纤的耦合效率解析表达式以及光纤端面相对于耦合系统存在横向偏移和端面倾斜时的耦合效率解析表达式。基于上述理论表达式计算了空间激光与光纤的耦合效率,并通过实验验证了此理论表达式的有效性。理论计算和实验均证实了单模阶跃光纤对于横向偏移更敏感,当横向偏移量等于单模光纤的纤芯半径时所对应的耦合效率只有20.25%,为理论最大值的1/4;而大模面积光子晶体光纤对于端面倾斜更加敏感,当端面倾斜2°时对应的耦合效率只有40.5%,为理论最大值的1/2。所提出理论表达式和实验方法完全可以为设计光纤耦合系统提供准确的参数。It is necessary to confirm the system parameters by theoretical analysis and experiments for desig- ning a optimum fiber-coupling system. By approximating the mode fields of a Single Mode Fiber（SMF） with a step index and a Photonic Crystal Fiber（PCF） with a Large Mode Area（LMA） using the Gaussian mode field, two analytical expressions for fiber-coupling efficiency in an ideal case and in the presences of lateral offset and fiber-end tilt are derived. Based on the two theoretical expressions, the efficiency for free-space laser coupling into the fibers is computed. Moreover, the validity of the two expressions are verified by experiments. As a re- sult, the theoretical computation and experiments demonstrate that the SMF with the step index is more sensirive to the lateral offset compared to the PCF. When the offset is equal to the radius of the fiber core, the effi- ciency is only 20. 25%, which is a quarter of the theoretical maximum efficiency. Besides, the PCF with the LMA is more sensitive to the fiber-end tilt. When the tilt angle is 2°, the efficiency is only 40.5%, which is a half of the theoretical maximum efficiency. In conclusion, the proposed theoretical expressions and experi- ments can provide accurate parameters for designing fiber-coupling systems.

关 键 词：单模光纤 光子晶体光纤 空间激光 光纤耦合 耦合效率 横向偏移 端面倾斜 

分 类 号：TN25[电子电信—物理电子学] TN249