School of Physics, State Key Lab for Mesoscopic Physics , Peking University , Beijing 100871 , China.
Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China.
ACS Nano. 2018 Apr 24;12(4):3908-3916. doi: 10.1021/acsnano.8b01380. Epub 2018 Apr 5.
The chiral state of light plays a vital role in light-matter interactions and the consequent revolution of nanophotonic devices and advanced modern chiroptics. As the light-matter interaction goes into the nano- and quantum world, numerous chiroptical technologies and quantum devices require precise knowledge of chiral electromagnetic modes and chiral radiative local density of states (LDOS) distributions in detail, which directly determine the chiral light-matter interaction for applications such as chiral light detection and emission. With classical optical techniques failing to directly measure the chiral radiative LDOS, deep-subwavelength imaging and control of circular polarization (CP) light associated phenomena are introduced into the agenda. Here, we simultaneously reveal the hidden chiral electromagnetic mode and acquire its chiral radiative LDOS distribution of a single symmetric nanostructure at the deep-subwavelength scale by using CP-resolved cathodoluminescence (CL) microscopy. The chirality of the symmetric nanostructure under normally incident light excitation, resulting from the interference between the symmetric and antisymmetric modes of the V-shaped nanoantenna, is hidden in the near field with a giant chiral distribution (∼99%) at the arm-ends, which enables the circularly polarized CL emission from the radiative LDOS hot-spot and the following active helicity control at the deep-subwavelength scale. The proposed V-shaped nanostructure as a functional unit is further applied to the helicity-dependent binary encoding and the two-dimensional display applications. The proposed physical principle and experimental configuration can promote the future chiral characterization and manipulation at the deep-subwavelength scale and provide direct guidelines for the optimization of chiral light-matter interactions for future quantum studies.
光的手性态在光物质相互作用以及随后的纳米光子器件和先进的现代手性学革命中起着至关重要的作用。随着光物质相互作用进入纳米和量子世界，许多手性技术和量子器件需要详细了解手性电磁模式和手性辐射局域密度态（LDOS）分布，这直接决定了手性光物质相互作用在诸如手性光探测和发射等应用中的作用。由于传统光学技术无法直接测量手性辐射 LDOS，因此将深亚波长成像和对圆偏振（CP）光相关现象的控制引入了议程。在这里，我们通过 CP 分辨的阴极发光（CL）显微镜同时揭示了隐藏的手性电磁模式，并获得了单个对称纳米结构的手性辐射 LDOS 分布，其深亚波长尺度。在垂直入射光激发下，由于 V 形纳米天线的对称模和反对称模之间的干涉，对称纳米结构的手性隐藏在近场中，在臂端具有巨大的手性分布（∼99%），从而使圆偏振 CL 发射来自辐射 LDOS 热点，并在深亚波长尺度下实现后续的主动螺旋控制。所提出的 V 形纳米结构作为功能单元进一步应用于螺旋相关的二进制编码和二维显示应用。所提出的物理原理和实验配置可以促进深亚波长尺度的手性表征和操纵，并为未来量子研究中手性光物质相互作用的优化提供直接指导。
