Localized surface plasmon polaritons can confine the optical field to a single-nanometer-scale area, strongly enhancing the interaction between photons and molecules. Theoretically, the ultimate enhancement might be achieved by reducing the “photon size” to the molecular extinction cross-section. In addition, desired control of electronic transitions in molecules can be realized if the “photon shape” can be manipulated on a single-nanometer scale. By matching the photon shape with that of the molecular electron wavefunction, optically forbidden transitions can be induced efficiently and selectively, enabling various unconventional photoreactions. Here, we demonstrate the possibility of forming single-nanometer-scale, highly intense fields of optical vortices using designed plasmonic nanostructures. The orbital and spin angular momenta provided by a Laguerre–Gaussian beam are selectively transferred to the localized plasmons of a metal multimer structure and then confined into a nanogap. This plasmonic nano-vortex field is expected to fit the molecular electron orbital shape and spin with the corresponding angular momenta.

中文翻译：

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手性光子的纳米整形

局部表面等离子体激元可以将光场限制在单纳米尺度的区域，强烈增强光子和分子之间的相互作用。从理论上讲，最终的增强可能是通过将“光子尺寸”减小到分子消光截面来实现的。此外，如果可以在单纳米尺度上操纵“光子形状”，则可以实现对分子中电子跃迁的理想控制。通过将光子形状与分子电子波函数的形状相匹配，可以有效和选择性地诱导光学禁止跃迁，从而实现各种非常规光反应。在这里，我们展示了使用设计的等离子体纳米结构形成单纳米级、高强度光学涡旋场的可能性。拉盖尔-高斯光束提供的轨道和自旋角动量被选择性地转移到金属多聚体结构的局部等离子体，然后被限制在纳米间隙中。这种等离子体纳米涡流场有望与分子电子轨道形状相匹配，并以相应的角动量自旋。