锥形透镜光纤聚焦特性研究

锥形透镜光纤(TLF)是实现光纤与平面光波光路(PLC)芯片高效耦合的核心元件。了解和掌握其聚焦特性是指导平面光波光路尾纤封装技术的关键。给出了表征锥形透镜光纤聚焦特性的两个参量出射光斑直径和远场发散角的理论分析模型,其误差小于1.14%;采用光束传播法数值模拟了锥形透镜光纤中的光波传输和模斑的演化,确定了锥形透镜光纤端面出射光斑的大小;优化锥形透镜光纤结构参量为:拉锥长度300μm,锥角0.733°,透镜曲率半径13.485μm;建立了基于数字摄像机的锥形透镜光纤出射光场测试系统,提出了物理光学反向推演法,计算出锥形透镜光纤聚焦光斑尺寸和远场发散角。理论与实验结果有着良好的一致:对于相同结构参量的锥形透镜光纤,实验反推法得到的出射光斑尺寸与理论值相比误差为3.15%,远场发散角误差为3.67%。

Investigation on Focusing Performance of Tapered and Lensed Fiber

Tapered and lensed fiber(TLF) is the key device to couple optical energy from optical fiber into planar lightwave circuits(PLC) high-efficiently. To understand and grasp TLF's focusing performance is pivotal for PLC pigtail packaging technology. The theoretical analysis model of output beam spot diameter and far-field divergence angle, which are principal parameters to represent TLF's focusing characteristics, is put forward. The error of the model falls within 1.14%. Lightwave propagation and mode field evolution are simulated by finite-difference beam propagation method so that the spot diameter is ascertained. TLF's taper length , half core taper angle, and lens curvature radius are optimized to be 300 μm, 0.733°, 13.485 μm respectively. The focusing beam spot is observed by digital video camera experimental setup and calculated using an inverse deducing method from physical optics. The theoretical and measurement results are consistent. For a specific TLF sample, the spot diameter value by inverse deducing method is differed from the theoretical one with error of 3.15%, and the error for far-field divergence angle is 3.67%.