Li Xu, Chen Zhigang, Taflove Allen, Backman Vadim
Opt Express. 2005 Jan 24;13(2):526-33. doi: 10.1364/opex.13.000526.
We report the phenomenon of ultra-enhanced backscattering of visible light by nanoparticles facilitated by the 3-D photonic nanojet - a sub-diffraction light beam appearing at the shadow side of a plane-waveilluminated dielectric microsphere. Our rigorous numerical simulations show that backscattering intensity of nanoparticles can be enhanced up to eight orders of magnitude when locating in the nanojet. As a result, the enhanced backscattering from a nanoparticle with diameter on the order of 10 nm is well above the background signal generated by the dielectric microsphere itself. We also report that nanojet-enhanced backscattering is extremely sensitive to the size of the nanoparticle, permitting in principle resolving sub-nanometer size differences using visible light. Finally, we show how the position of a nanoparticle could be determined with subdiffractional accuracy by recording the angular distribution of the backscattered light. These properties of photonic nanojets promise to make this phenomenon a useful tool for optically detecting, differentiating, and sorting nanoparticles.
我们报道了由三维光子纳米射流促成的纳米颗粒对可见光的超增强背散射现象，三维光子纳米射流是一种出现在平面波照射的介电微球阴影侧的亚衍射光束。我们严格的数值模拟表明，当纳米颗粒位于纳米射流中时，其背散射强度可增强高达八个数量级。因此，直径约为10纳米的纳米颗粒增强后的背散射远高于介电微球本身产生的背景信号。我们还报道，纳米射流增强背散射对纳米颗粒的尺寸极其敏感，原则上允许使用可见光分辨亚纳米尺寸差异。最后，我们展示了如何通过记录背散射光的角分布以亚衍射精度确定纳米颗粒的位置。光子纳米射流的这些特性有望使这一现象成为光学检测、区分和分选纳米颗粒的有用工具。
