Department of Physics and London Centre for Nanotechnology, King's College London, Strand, London, WC2R 2LS, United Kingdom.
Phys Rev Lett. 2018 Nov 9;121(19):193901. doi: 10.1103/PhysRevLett.121.193901.
We propose a method for ultrasensitive displacement and phase measurements based on a nanoantenna illuminated with interfering evanescent waves. We show that with a proper nanoantenna design, tiny displacements and relative phase variations can be converted into changes of the scattering direction in the Fourier space. These sensitive changes stem from the strong position dependence of the orientation of the purely imaginary Poynting vector produced in the interference pattern of evanescent waves. Using strongly confined evanescent standing waves, high sensitivity is demonstrated on the nanoantenna's zero-scattering direction, which varies linearly with displacement over a wide range. With weakly confined evanescent wave interference, even higher sensitivity to tiny displacement or phase changes can be reached near a particular location. The high sensitivity of the proposed method can form the basis for many metrology applications. Furthermore, this concept demonstrates the importance of the imaginary part of the Poynting vector, a property that is related to reactive power and is often ignored in photonics.
我们提出了一种基于纳米天线的超灵敏位移和相位测量方法，该方法利用干涉消逝波进行照明。我们表明，通过适当的纳米天线设计，可以将微小的位移和相对相位变化转换为傅里叶空间中散射方向的变化。这些灵敏的变化源于消逝波干涉图案中产生的纯虚 Poynting 矢量方向的强烈位置依赖性。利用强限制的消逝驻波，在纳米天线的零散射方向上展示了高灵敏度，该灵敏度在很大范围内随位移线性变化。利用弱限制的消逝波干涉，可以在特定位置附近达到对微小位移或相位变化的更高灵敏度。所提出方法的高灵敏度可以为许多计量学应用提供基础。此外，该概念证明了 Poynting 矢量虚部的重要性，这一性质与无功功率有关，在光子学中经常被忽略。
