Department of Electrical and Electronics Engineering, İzmir Katip Çelebi University, 35620 Çiğli, İzmir, Turkey.
Opt Lett. 2012 Jun 15;37(12):2313-5. doi: 10.1364/OL.37.002313.
We analyze the far-field resolution of apertures that are illuminated by a point dipole located at subwavelength distances. It is well known that radiation emitted by a localized source can be considered a combination of traveling and evanescent waves, when represented by the angular spectrum method. The evanescent wave part of the source can be converted to propagating waves by diffraction at the aperture; thereby it contributes to the far-field detection. Therefore one can expect an increase in the resolution of objects. We present explicit calculations showing that the resolution at the far zone is improved by decreasing the source-aperture distance. We also utilize the resolution enhancement by the near field of a dipole to resolve two closely located apertures. The results show that without the near field (evanescent field) the apertures are not resolved, whereas with the near field of the dipole the far zone intensity distribution shows improved resolution. This method eliminates the requirements of near-field techniques such as controlling and scanning closely located tip detectors.
我们分析了在亚波长距离处位于点偶极子照射下的孔径的远场分辨率。众所周知，当通过角谱方法表示时，局部源发射的辐射可以被视为传播波和消逝波的组合。源的消逝波部分可以通过在孔径处的衍射转换为传播波，从而有助于远场检测。因此，可以预期物体的分辨率会提高。我们提出了明确的计算结果，表明通过减小源孔距离可以提高远场的分辨率。我们还利用偶极子近场的分辨率增强来分辨两个紧密排列的孔。结果表明，如果没有近场（消逝场），则无法分辨孔，而在偶极子的近场中，远场强度分布显示出改善的分辨率。该方法消除了近场技术（例如控制和扫描紧密相邻的尖端探测器）的要求。
