CAREER: Digital plasmonics-based nano-tweezing and nano-imaging for nano-particles

光是一种非常强大的工具，可以探测、成像，甚至操纵小物体。不幸的是，由于光是一种波，它受到衍射的限制，或所有波向外扩散的趋势。因此，非常小的纳米级物体，如细胞、单个分子、病毒和纳米设备的基本成分，都太小了，无法单独探测、操纵和直接用光成像。然而，“等离子体”领域允许在金属纳米结构表面以亚波长精度操纵光。等离子体激元可以将其光能压缩到~10纳米的空间中，这是直接与这些金属表面上或附近的纳米级物体相互作用的理想尺寸。对等离子体的精确操作需要光的仔细照射和极其灵敏的光学记录设备。PI具有数字和计算技术的能力：(1)在计算机控制下激发等离子体直接操纵纳米物体；(2)仔细记录等离子体的行为，直接成像纳米物体的形状、大小和厚度。这些数字技术将为科学家在精确的计算机控制下直接研究、探测、成像、操纵和与纳米级物体（如DNA、蛋白质分子、量子点、病毒或纳米颗粒）相互作用开辟新的机会。此外，由于这项研究是专门由本科生进行的，它有望激励、激励和培养许多新的年轻科学家和工程师。数字技术的出现明确地模拟了光的传播，通过“数字全息显微镜”和“计算机生成全息”彻底改变了光学成像和光学镊子。与传统光学技术相比，这些技术具有许多优点，例如：(1)成像或产生完整的复杂波；(2)无运动部件的快速光束扫描；(3)动态操纵受困物体；(4)通过散射介质消除像差和成像；(5)自由选择任何成像方式，例如相位对比和幅度对比。不幸的是，这些强大的数字技术还没有在近场光学中完全实现，特别是在等离子体光学中。事实上，等离子体纳米成像和纳米镊子最近引起了人们对捕获、探测、操纵和成像纳米级物体（如病毒、纳米颗粒和单个分子）的极大兴趣。因此，将强大的数字光学技术引入近场有望产生巨大的影响。具体来说，空间光调制器将用于产生计算机控制的紧密聚焦等离子体，用于纳米镊子和高空间频率等离子体场，用于超分辨率成像。等离子体波的相位也将通过直接在纳米金属衬底上设计干涉仪或通过记录反射或透射光的数字全息图来成像。这两种技术将实现重要的新功能，如：(1)超分辨率，高速等离子体相衬成像，以成像生物结构的厚度；(2)捕获和实时操作纳米物体，用于纳米制造或分类；(3)捕获纳米物体的光学探测，用于单分子的光谱表征。

Light is an extremely powerful tool to probe, image, and even manipulate small objects. Unfortunately, since light is a wave it is limited by diffraction, or the tendency of all waves to spread out. As a result very small nano-sized objects like the basic components of cells, single molecules, viruses, and nano-devices are too small to beindividually probed, manipulated, and imaged directly with light. However, the field of 'plasmonics' allows manipulating light with sub-wavelength precision at the surface of metallic nano-structures. Plasmons can squeeze their optical energy into ~10 nanometer spaces, an ideal size for directly interacting with nano-sized objects that are on or near these metallic surfaces. Precise manipulation of plasmons requires careful illumination with light, and extremely sensitive optical recording equipment. PI has the capability of digital and computational techniques to both: (1) excite plasmons to directly manipulate nano-objects under computer control; and (2) carefully record the behavior of plasmons to directly image the shape, size, and thickness of nano-objects. These digital techniques will open up new opportunities for scientists under precise computer control to directly study, probe, image, manipulate, and interact with nano-sized objects such as DNA, protein molecules, quantum dots, viruses, or nanoparticles. Furthermore, since this research is being performed exclusively with undergraduate students, it promises to inspire, motivate, and train many new young scientists and engineers.The emergence of digital techniques that explicitly model the propagation of light has revolutionized optical imaging and optical tweezing through 'digital holographic microscopy' and 'computer generated holography'. These techniques offer many advantages over conventional optics such as: (1) imaging or generating the full complex wave; (2) fast beam scanning with no moving parts; (3) dynamic manipulation of trapped objects; (4) eliminating aberrations and imaging through scattering media; and (5) freedom to choose any imaging modality, e.g. phase vs. amplitude contrast. Unfortunately, these powerful digital techniques have not yet been fully realized in near-field optics, and in particular, with plasmons. Indeed, plasmonic nano-imaging and nano-tweezing have recently generated immense interest to trap, probe, manipulate, and image nano-sized objects such as viruses, nanoparticles, and individual molecules. Therefore, introducing powerful digital optical techniques into the near-field promises to have a large impact. Specifically, a spatial light modulator will be used to generate computer-controlled, tightly focused plasmons for nano-tweezing and high-spatial frequency plasmonic fields for super-resolution imaging. The phase of the plasmon waves will also be imaged by designing interferometers directly into the nano-metallic substrates or by recording a digital hologram of the reflected or transmitted light. These two techniques will enable significant new capabilities such as: (1) super-resolution, high-speed plasmonic phase-contrast imaging to image the thickness of biological structures; (2) trapping and real-time manipulation of nano-metric objects for nanofabrication or sorting; and (3) optical probing of trapped nano-objects for spectroscopic characterization of single molecules.