Converging Microlens Array Using Nematic Liquid Crystals Doped with Chiral Nanoparticles
Converging Microlens Array Using Nematic Liquid Crystals Doped with Chiral Nanoparticles
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DOI：
10.1021/acsami.0c21044
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发表时间：
2021-01-07
影响因子：
9.5
通讯作者：
Jakli, Antal
中科院分区：
文献类型：
--
作者：
Perera, Kelum;Nemati, Ahlam;Jakli, Antal
非手性分子的向列型液晶或手性分子的外消旋混合物悬浮在亚毫米大小的网格中并浸没在水中时形成平坦的膜。最近，已经表明（Popov等人，2017），掺杂有手性分子的双折射液晶的膜在水下采用双凸透镜形状。弯曲形状与退化平面锚定一起导致光轴沿膜平面沿着径向变化，提供了改变几何光学成像的Pancharatnam-Berry型相位透镜。在这里，我们描述了通过添加手性纳米颗粒形成的向列型手性配体液晶微透镜。结果表明，纳米粒子的螺旋扭曲力比最强的分子手性掺杂剂的螺旋扭曲力大400 μ m（-1），是形成透镜的关键因素。我们展示了成像能力和测量的形状，以及手性纳米粒子掺杂的液晶透镜的焦距。我们表明，测量的透镜的形状允许一个计算的手性双折射液晶的螺距，从而确定的手性配体封端的纳米粒子的螺旋扭转功率。这样的测量仅需要使用纳克的手性纳米颗粒，这比常规技术所需的少3个数量级。由于NP对诸如光和电场以及磁场的外部刺激敏感，因此手性NP的使用可以允许实现这种微透镜阵列的可调谐光学性质。
Nematic liquid crystals of achiral molecules or racemic mixtures of chiral ones form flat films when suspended in submillimeter size grids and submerged under water. Recently, it has been shown (Popov et al., 2017) that films of nematic liquid crystals doped with chiral molecules adopt biconvex lens shapes underwater. The curved shape together with degenerate planar anchoring leads to a radial variation of the optical axis along the plane of the film, providing a Pancharatnam-Berry-type phase lens that modifies geometric optical imaging. Here, we describe nematic Chiral ligand liquid crystal microlenses formed by the addition of chiral nanoparticles. It is found that the helical twisting power of the nanoparticles, the key factor to form the lens, is about 400 mu m(-1) greater than that of the strongest molecular chiral dopants. We demonstrate imaging capabilities and measure the shape as well as the focal length of the chiral nanoparticle-doped liquid crystal lens. We show that measuring the shape of the lens allows one to calculate the helical pitch of the chiral nematic liquid crystal and thus determine the helical twisting power of the chiral ligand-capped nanoparticles. Such measurements require the use of only nanograms of chiral nanoparticles, which is 3 orders of magnitude less than that required by conventional techniques. Since NPs are sensitive to external stimuli such as light and electric and magnetic fields, the use of chiral NPs may allow the achievement of tunable optical properties for such microlens arrays.