Department of Physics and Astronomy, Trent University, Peterborough, ON, Canada K9L 0G2.
Department of Physics, Concordia University, Montreal, QC, Canada H4B 1R6.
Proc Natl Acad Sci U S A. 2019 Mar 5;116(10):4000-4005. doi: 10.1073/pnas.1818350116. Epub 2019 Feb 19.
The sparking of cut grape hemispheres in a household microwave oven has been a poorly explained Internet parlor trick for over two decades. By expanding this phenomenon to whole spherical dimers of various grape-sized fruit and hydrogel water beads, we demonstrate that the formation of plasma is due to electromagnetic hotspots arising from the cooperative interaction of Mie resonances in the individual spheres. The large dielectric constant of water at the relevant gigahertz frequencies can be used to form systems that mimic surface plasmon resonances that are typically reserved for nanoscale metallic objects. The absorptive properties of water furthermore act to homogenize higher-mode profiles and to preferentially select evanescent field concentrations such as the axial hotspot. Thus, beyond providing an explanation for a popular-science phenomenon, we outline a method to experimentally model subwavelength field patterns using thermal imaging in macroscopic dielectric systems.
二十多年来，家用微波炉中切开的葡萄半球的火花一直是一个解释不清的互联网小把戏。通过将这一现象扩展到各种葡萄大小的水果和水凝胶珠的整个球形二聚体，我们证明等离子体的形成是由于单个球体中的米氏共振的协同相互作用产生的电磁热点。在相关千兆赫频率下，水的大介电常数可用于形成模拟通常保留给纳米级金属物体的表面等离激元共振的系统。水的吸收特性进一步起到均匀化高阶模式轮廓和优先选择消逝场浓度（如轴向热点）的作用。因此，除了为一个科普现象提供解释之外，我们还概述了一种使用宏观介电系统中的热成像来实验模拟亚波长场模式的方法。
