High Quality Factor Dielectric Metasurfaces for Ultraviolet Circular Dichroism Spectroscopy
High Quality Factor Dielectric Metasurfaces for Ultraviolet Circular Dichroism Spectroscopy
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DOI：
10.1021/acsphotonics.9b01352
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发表时间：
2020-01-01
期刊：
影响因子：
7
通讯作者：
Dionne, Jennifer A.
中科院分区：
文献类型：
--
作者：
Hu, Jack;Lawrence, Mark;Dionne, Jennifer A.
手性光谱学，如圆二色性，在生物医学、制药和农用化学工业中对于揭示分子的结构信息和确定化学样品的纯度至关重要。新兴的纳米光子平台已被证明通过光学手性C的局部密度浓度增加了圆偏振光与手性分子之间的内在弱相互作用。然而，C的增强仅限于红外和可见光频率，而大多数小分子的手性吸收特征是在紫外线。此外，纳米光子系统中可实现的C增强仍然相对较低，特别是在整个样品体积上平均时。在这里，我们使用全场模拟来设计一个高质量因子（高Q）的金刚石超表面，它在紫外线下将C提高了3个数量级以上。金刚石纳米结构可以实现紫外米氏共振，而双周期圆盘晶格可以激活高Q共振，从而显着增加电磁场强度。当高Q电偶极子和磁偶极子模式在空间和光谱上重叠时，会出现一种类似kerker的条件，使局部的均匀符号C增强高达1130倍。即使在距离表面40纳米的单位电池上平均，C的增强也超过100倍。我们展示了如何通过双周期晶格中的直径偏移调整结构不对称性来进一步调整质量因子和C。我们的研究结果为超灵敏手性光谱和高效光介导对映体分离铺平了道路。
Chiral-optical spectroscopies, such as circular dichroism, are critical in the biomedical, pharmaceutical, and agrochemical industries for revealing structural information about molecules and determining the purity of chemical samples. Emerging nanophotonic platforms have been shown to increase the intrinsically weak interaction between circularly polarized light and chiral molecules through the concentration of the local density of optical chirality, C. However, enhancements in C have been limited to infrared and visible frequencies, while the chiral absorption features of most small molecules are in the ultraviolet. Furthermore, achievable C enhancements in nanophotonic systems remain relatively low, especially when averaged across the sample volume. Here, we use full-field simulations to design a high quality factor (high Q) diamond metasurface that enhances C by over 3 orders of magnitude in the ultraviolet regime. The diamond nanostructures enable ultraviolet Mie resonances while a biperiodic disk lattice activates high Q resonances that significantly increase the electromagnetic field intensities. When a high Q electric dipole and magnetic dipole mode are spatially and spectrally overlapped, a Kerker-like condition emerges that enables uniform sign C enhancements that are locally as high as 1130-fold. Even when averaged across the unit cell and 40 nm away from the surface, enhancements in C exceed 100-fold. We show how the quality factor and C can be further tuned by adjusting the structural asymmetry via the diameter offset in the biperiodic lattice. Our results pave the way for ultrasensitive chiral spectroscopy and efficient light-mediated enantiomer separation.