通过硅纳米盘的纵向Mie共振增强的光学手性分离
Enhanced Enantioselective Optical Trapping enabled by Longitudinal Mie Resonances in Silicon Nanodisks
AI总结：
利用硅纳米盘的纵向Mie共振实现高选择性的光学手性分离与捕获
摘要：
纳米尺度物质的光学手性分离本质上受到固有弱手性力相对于主导的非手性梯度力和热波动的限制。传统等离子体方法通常通过增强手性而放大非手性吸引力和加热。在这里，我们通过利用硅纳米盘的纵向Mie共振克服了这种权衡。通过采用方位-径向极化光束（ARPB）照明，我们选择性地激发纵向Mie共振，具有强光学手性梯度和相对均匀的电场强度。具体而言，磁四极共振（MQ）共振有效将手性选择力与非手性背景分离，为手性光学捕获提供了独特的有利条件。结合全波模拟与克拉默斯逃逸率理论，我们展示了一个稳健的捕获系统，该系统既热稳定又高度选择性。我们预测对于具有Pasteur参数|κ|≥0.03的粒子，捕获选择比超过100，并且即使对于弱手性分析物（|κ|≈0.006），选择性仍保持在2以上。这些结果确立了在高折射率介质纳米结构中的纵向Mie共振作为所有光学手性分析和对映体分离的有前景的非侵入式平台。
英文摘要：
Optical enantioseparation of nanoscale matter is fundamentally limited by the intrinsic weakness of chiroptical forces compared to the dominant achiral gradient forces and thermal fluctuations. Conventional plasmonic approaches typically enhance chirality at the cost of amplifying achiral attraction and heating. Here, we overcome this trade-off by exploiting longitudinal Mie resonances in silicon nanodisks. By employing an Azimuthally-Radially Polarized Beam (ARPB) illumination, we selectively excite longitudinal Mie resonances, with strong optical chirality gradients and comparatively uniform electric field intensities. Specifically, magnetic quadrupole (MQ) resonances, effectively decouple enantioselective forces from the achiral background, providing uniquely favorable conditions for enantioselective optical trapping. Combining full-wave simulations with Kramers' escape-rate theory, we demonstrate a robust trapping system that is both thermally stable and highly selective. We predict trapping selectivity ratios above 100 for particles with Pasteur parameters $|κ| \geq$ 0.03 and maintain selectivities above 2 even for weakly chiral analytes ($|κ| \approx$ 0.006). These results establish longitudinal Mie resonances in high-index dielectric nanostructures as a promising, non-invasive platform for all-optical chiral analysis and enantiomer separation.
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