小芯径折射率引导型光子晶体光纤的制备和研究

介绍一种小芯径折射率引导型光子晶体光纤(PCF)的拉制方法.制备出的光纤纤芯周围第一层空气孔发生形变,呈柚子形,其芯径为1.7μm,孔间距A和空气孔直径d分别为3.4 μm和2.8μm.由于光纤结构的特殊性,采用有限元法在200～1600 nm波段对其基模有效折射率、色散系数、有效模场面积以及非线性系数进行了数值模拟计算.经过理论计算,这种光纤在所研究的波段具有极高的非线性系数且表现为反常色散,这些特性十分有利于超连续谱的产生.在测量了光纤的损耗、色散等基本特性后,选取损耗较小凡位于光纤反常色散区域,中心波长为800 nm的飞秒激光作为光源,将不同功率的超短激光脉冲耦合入光纤,对这种小芯径折射率引导型光子晶体光纤产生超连续谱的过程进行了测量和分析.

Fabrication and Study on the Small-Core Index-Guiding Photonic Crystal Fiber

A way of fabricating a small-core index-guiding photonic crystal fiber (PCF) is introduced. The first ring of the air holes around the core is deformed, the shape of which is similar to the grapefruit, and the diameter of the core is 1.7 μm; the pitch and diameter of the air hole are 3.4 μm and 2.8 μm, respectively. Because of the special structure of the fiber, the effective refractive indices, dispersion coefficients of the fundamental modes, effective areas and nonlinear coefficients of the fiber are calculated by finite element method from 200 nm to 1600 nm. The results show that, in this wavelength range, the nonlinear coefficients of this fiber are extremely high and dispersion coefficients are positive. These characteristics are of benefit to the supercontinuum generating. After measuring the dispersion and loss properties of the fiber, the laser operating wavelength in 800 nm is chosen to be the light source because the loss in this wavelength is lower and the central wavelength of the pulse is in the range of abnormal dispersion. The femtosecond pulses with different powers are coupled into this small-core index-guiding photonic crystal fiber. The supercontinuum generating in the fiber is detected and analyzed.