Zheng Lichao, Maqbool Esha, Han Zhanghua
Shandong Provincial Key Laboratory of Optics and Photonic Devices, Center of Light Manipulation and Applications, School of Physics and Electronics, Shandong Normal University, Jinan 250358, China.
Micromachines (Basel). 2024 Mar 25;15(4):437. doi: 10.3390/mi15040437.
Current optical tweezering techniques are actively employed in the manipulation of nanoparticles, e.g., biomedical cells. However, there is still huge room for improving the efficiency of manipulating multiple nanoparticles of the same composition but different shapes. In this study, we designed an array of high-index all-dielectric disk antennas, each with an asymmetric open slot for such applications. Compared with the plasmonic counterparts, this all-dielectric metasurface has no dissipation loss and, thus, circumvents the Joule heating problem of plasmonic antennas. Furthermore, the asymmetry-induced excitation of quasi-bound states in continuum (QBIC) mode with a low-power intensity (1 mW/µm) incidence imposes an optical gradient force of -0.31 pN on 8 nm radius nanospheres, which is four orders of magnitude stronger than that provided by the Fano resonance in plasmonic antenna arrays, and three orders of magnitude stronger than that by the Mie resonance in the same metasurface without any slot, respectively. This asymmetry also leads to the generation of large optical moments. At the QBIC resonance wavelength, a value of 88.3 pN-nm will act on the nanorods to generate a rotational force along the direction within the disk surface but perpendicular to the slot. This will allow only nanospheres but prevent the nanorods from accurately entering into the slots, realizing effective sieving between the nanoparticles of the two shapes.
当前，光镊技术被积极应用于纳米粒子的操控，例如生物医学细胞。然而，在操控相同成分但不同形状的多个纳米粒子的效率提升方面，仍有很大空间。在本研究中，我们设计了一种高折射率全介质圆盘天线阵列，每个天线都有一个不对称开口槽用于此类应用。与等离子体对应物相比，这种全介质超表面没有耗散损耗，因此避免了等离子体天线的焦耳热问题。此外，在低功率强度（1 mW/µm）入射下，连续体中准束缚态（QBIC）模式的不对称诱导激发在半径为8 nm的纳米球上施加了-0.31 pN的光学梯度力，这分别比等离子体天线阵列中的法诺共振提供的力强四个数量级，比同一无任何槽的超表面中的米氏共振提供的力强三个数量级。这种不对称还导致产生大的光学矩。在QBIC共振波长处，88.3 pN-nm的值将作用于纳米棒，以产生沿圆盘表面内但垂直于槽的方向的旋转力。这将只允许纳米球进入，而阻止纳米棒准确进入槽中，从而实现两种形状纳米粒子之间的有效筛分。
