用时阈有限差分方法研究光纤微探针近场分布特性

采用三维时间域有限差分（FDTD）方法研究了扫描近场光学显微镜中光纤微探针的近场分布特性，研究结果表明，锥形裸光纤探针的近场光中，以从探针锥变区侧面泄露的光即传播场为主，当在探针的侧面镀上一层金属膜对于从侧面泄露的光具有较好屏蔽效果，因而比裸光纤探针具有更好的空间束缚能力，无论是裸光纤探针还是金属膜探针，入射偏振光从针尖出射手发生了退极化现象，近场分布中产生与入射光偏振方向垂直的其它两个电场分量，而且金属膜探针的退极化分量对近场分布的影响比裸探针显著得多，如果在近场成像中接收退极化分量而不是总场则可以提高近场成像的对比度，还详细地分析了微探针的近场分布特征与退极化之间的关系。

Characterization of Near-Field Distribution of Optical Fiber Probe by FDTD

The near field distribution of uncoated and metal coated fiber optic probes were characterized by the method of three dimensional finite difference time domain (FDTD). The result reveals that, for an uncoated probe, propagating wave emitting from the conic side dominates the near field distribution, while a film of metal is coated, the coated probe can confine the wave more strictly inside it. Second, the polarized incident wave becomes depolarized after emitting from the small aperture of two kinds of probes. In other words, there are two electric field components whose polarization direction is perpendicular to that of the incident one. Accordingly, the image contrast can be improved if the polarized components instead of the total field are detected. The relationship between the distribution characteristics of near field distribution and the phenomenon of depolarization is analyzed in detail.