Droulias Sotiris, Bougas Lykourgos
Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete, Greece.
Department of Materials Science and Technology, University of Crete, 70013 Heraklion, Greece.
Nano Lett. 2020 Aug 12;20(8):5960-5966. doi: 10.1021/acs.nanolett.0c01938. Epub 2020 Jul 7.
Sensing molecular chirality at the nanoscale has been a long-standing challenge due to the inherently weak nature of chiroptical signals, and nanophotonic approaches have proven fruitful in accessing these signals. However, in most cases, complete sensing of the chiral part of the molecule's refractive index (magnitude and sign of both its real and imaginary part) has not been possible, while the strong inherent signals from the nanostructures themselves obscure the weak chiroptical signals. Here, we propose a dielectric metamaterial system that overcomes these limitations and allows for complete measurements of the total chirality and discrimination of the effects of its real and imaginary part, possible also in an absolute manner via the application of a crucial signal reversal (excitation with reversed polarization) that enables chirality measurements without the need for sample removal. As proof of principle, we demonstrate signal enhancements by a factor of 200 for ultrathin, subwavelength, chiral samples over a uniform and accessible area.
由于手性光学信号本质上较弱，在纳米尺度上感知分子手性一直是一个长期存在的挑战，而纳米光子学方法已被证明在获取这些信号方面卓有成效。然而，在大多数情况下，尚未能够完整地感知分子折射率的手性部分（其实部和虚部的大小及符号），同时纳米结构本身强烈的固有信号掩盖了微弱的手性光学信号。在此，我们提出一种介电超材料系统，该系统克服了这些限制，能够对总手性进行完整测量，并区分其实部和虚部的影响，通过应用关键的信号反转（反向极化激发）还能够以绝对的方式实现这一点，从而无需移除样品即可进行手性测量。作为原理验证，我们展示了在均匀且可及的区域内，超薄、亚波长手性样品的信号增强了200倍。
