Liao Meisong, Gao Weiqing, Duan Zhongchao, Yan Xin, Suzuki Takenobu, Ohishi Yasutake
Research Center for Advanced Photon Technology, Toyota Technological Institute, Tempaku, Nagoya, Japan.
Opt Express. 2012 Jan 16;20(2):1141-50. doi: 10.1364/OE.20.001141.
We demonstrate theoretically and experimentally that it is feasible to draw the microstructured fiber with longitudinally varying diameter (FLVD) whose diameter varies sharply in a short fiber length. It is elucidated that during the fiber drawing process the tension is linearly proportional to the natural logarithm of the fiber drawing speed. As a result, the tension is not so sensitive to the fiber diameter. Moreover, this sensitivity can be decreased by using a large diameter ratio of preform to fiber. Owing to the low sensitivity the FLVD with diameter varying sharply in a short fiber length can be drawn directly from the preform. Additionally we show that the microstructural geometry of FLVD does not depend on the varying diameter. The deformation in microstructural geometry is determined by the fiber segment with the smallest diameter. We fabricate a FLVD of which the diameter decreases by 75% in a fiber length of 10 cm. By using this fiber we demonstrate the 600-1800 nm supercontinuum (SC) generation and the 532 nm second harmonic generation pumped by a picosecond fiber laser. The SC spectra by the conventional fibers with the largest and the smallest diameters of the FLVD are also shown, respectively. The comparisons show that the FLVD has the broadest SC spectrum due to its high nonlinearity, varying dispersion, and high damage threshold.
我们通过理论和实验证明，拉制一种在短纤维长度内直径急剧变化的纵向变径微结构光纤（FLVD）是可行的。结果表明，在光纤拉丝过程中，张力与拉丝速度的自然对数呈线性比例关系。因此，张力对光纤直径不太敏感。此外，通过使用较大的预制棒与光纤直径比，可以降低这种敏感性。由于敏感性较低，可以直接从预制棒拉制出在短纤维长度内直径急剧变化的FLVD。此外，我们还表明，FLVD的微观结构几何形状不取决于变化的直径。微观结构几何形状的变形由直径最小的光纤段决定。我们制作了一种FLVD，其在10厘米的纤维长度内直径减小了75%。通过使用这种光纤，我们展示了由皮秒光纤激光器泵浦产生的600 - 1800纳米超连续谱（SC）和532纳米二次谐波产生。还分别展示了FLVD中直径最大和最小的传统光纤产生的SC光谱。比较结果表明，由于其高非线性、变化的色散和高损伤阈值，FLVD具有最宽的SC光谱。
