金属覆层光纤探针近场特性研究

采用有限积分法对用于近场光学显微镜的旋转对称光纤探针进行了数值模拟计算,研究了光纤探针开口附近亚波长范围的电磁场及其能量密度的分布.计算结果表明,在探针外,光场为沿探针轴线方向的近逝波,其空间光场的分布与激励光场及其极化方向有关,在激励光场的极化方向出现了由感应电荷引起的边缘增强效应.同时研究了近场光纤探针的空间分辨率和样品处的电磁场能量,结果表明光纤探针孔的尺寸及其与样品的作用距离是影响探针的分辨率和样品内电磁场能量的重要因素.

Study on the Optical Near Field of Metal-clad Optical Fiber Probes

Distributions of the near-field electromagnetic field and its energy density of rotationally symmetrical optical fiber probes used in scanning near-field optical microscopes (SNOM) are numerically studied using finite integration method (FIM). The results indicate that an evanescent wave exists out of the probe and that the polarization direction of the near field is related to that of the excitation field of the fiber probe. An edge enhancement effect,caused by the induced charges on the surface of metal cover,is observed along the polarization direction. The computed results also prove that the resolution of the probe and the electromagnetic energy within the samples are mainly determined by the aperture size of the probe and the distance between the sample and the probe aperture.