Li Lingli, Fu Yongqi, Wu Hongsheng, Zheng Ligong, Zhang Hongxin, Lu Zhenwu, Sun Qiang, Yu Weixing
Graduate School of the Chinese Academy of Sciences, Beijing, 10039, China.
Opt Express. 2011 Sep 26;19(20):19365-73. doi: 10.1364/OE.19.019365.
The Talbot effect of an Ag nanolens with five periodic concentric rings that are illuminated by the radially polarized light was numerically studied by means of rigorous finite-difference and time-domain (FDTD) algorithm. It was found that the Talbot effect occurs only when the incident wavelength is at the scale of less than half of period of the grating structures of the nanolenses. Specifically, in this work, the nanolenses with a 500 nm period grating structures has five focal points due to Talbot effect for the incident wavelength of λ = 248 nm. The diameter of the first focal spot after the exit plane in free space is 100 nm. In contrast, we analyzed the corresponding focal points on the basis of Talbot self-imaging by scalar diffraction theory. It was found that the scalar Talbot effect cannot interpret the Talbot effect phenomenon for the metallic nanolenses. It may attribute to the paraxial approximation applied in the Talbot effect theory in far-field region. However, the approximation does not hold in our nanolenses structures during the light propagation. In addition, the Talbot effect appears at the short-wavelength regime only, especially in the ultraviolet wavelength region.
利用严格的时域有限差分（FDTD）算法对具有五个周期性同心环的银纳米透镜在径向偏振光照射下的塔尔博特效应进行了数值研究。结果发现，只有当入射波长小于纳米透镜光栅结构周期的一半时，才会出现塔尔博特效应。具体而言，在本工作中，对于周期为500 nm光栅结构的纳米透镜，由于波长为λ = 248 nm的入射光的塔尔博特效应，其具有五个焦点。自由空间中出射平面后的第一个焦斑直径为100 nm。相比之下，我们基于标量衍射理论的塔尔博特自成像分析了相应的焦点。结果发现，标量塔尔博特效应无法解释金属纳米透镜的塔尔博特效应现象。这可能归因于远场区域塔尔博特效应理论中应用的傍轴近似。然而，在我们的纳米透镜结构中，光传播过程中该近似并不成立。此外，塔尔博特效应仅出现在短波长区域，特别是在紫外波长区域。
