RUI: Unraveling Novel Nanophotonic Effects in Mid-Index Micro-Sized Dielectric Materials

非技术总结：当光与物质相互作用时，会发生许多事情——它可以被吸收、反射、散射或传输。如果物质具有纳米级的特征，光与物质的相互作用就会产生有趣的现象。例如，光学模拟可以将光能限制在纳米结构的体积内。在零反向散射（ZBS）的情况下，光优先在正向散射。新兴的纳米光子学领域将这种现象应用于太阳能、成像、医学、光通信和数据存储等领域。然而，对这些新型纳米光子效应的观察目前仅限于具有高折射率的材料，如硅和锗，并且需要纳米尺度的特征尺寸。伊利诺伊州立大学（ISU）的研究小组计划在中等指数材料中证明这些效应，如二氧化钛和钻石，具有微米尺度的特征。这项研究将推动材料的可用性及其尺寸的界限，远远超出目前观察这些新型纳米光子效应的限制。从长远来看，从该团队的研究中获得的知识可以用于开发更有效的光学和光子设备，如光电探测器和纳米激光器。PI将通过培训本科学生进行研究，并将研究项目的成果整合到物理课程中，从而扩大光学和光子学领域的劳动力。通过利用现有的ISU基础设施招募和培训代表性不足的学生，包括与当地高中生的联系，鼓励代表性不足的少数民族参与STEM。技术概述：高折射率介电粒子的共振光学激发为展示新型纳米光子效应提供了独特的机会，如非辐射拟极点状态、最佳正向散射和磁热点增强的珀塞尔效应。观察到的这些新型纳米光子效应与高折射率无损介电材料中单偶极模式的激发有关。由于平面波照射下高阶多极模的贡献，这些效应在微尺度物体上是无法实现的。因此，纳米光子效应的观察目前仅限于在纳米尺寸范围内的一些相对高折射率的材料-通常在硅和锗中。最近从理论上预测，在光照下，人们可以解开具有宽尺寸参数和折射率的均匀高折射率球体的偶极态。伊利诺伊州立大学（ISU）的研究小组计划通过实验解开偶极态，激发非辐射拟极态，并在紧密聚焦的高斯光束（tfgb）照射下，在微米范围内的中折射率（1.5 n 3.0）介电球中证明零后向散射。tfgb有选择地激发几个相关的Mie系数，并控制入射场不同多极模的相对权重。这种方法将使研究人员能够解开中折射率下微尺度均匀球中的偶极态和相关的新型纳米光子效应。理解这些现象为纳米光子相关应用的材料和物体的可用性提供了巨大的可能性，这些材料和物体的尺寸参数远远超出了当前的物理图像。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY:When light interacts with matter, a number of things can happen – it can be absorbed, reflected, scattered, or transmitted. If matter has nanoscale features, light-matter interactions can lead to interesting phenomena. For example, optical anapoles can confine light energy within the volume of nanostructures. In the case of zero back scattering (ZBS), light is preferentially scattered in the forward direction. The emerging field of nanophotonics puts such phenomena to use in applications such as solar energy, imaging, medicine, optical communications, and data storage. However, observation of these novel nanophotonic effects is currently restricted to materials with a high refractive index, such as silicon and germanium, and requires features sizes on the nanometer scale. The research team at Illinois State University (ISU) plans to demonstrate these effects in mid-index materials, such as titanium dioxide and diamond, with micrometer scale features. This research will push the boundary in terms of availability of materials and their size well beyond the current limit for observation of these novel nanophotonic effects. In the long run, the knowledge gained from the team’s research could be used to develop more efficient optical and photonic devices, such as photodetectors and nanolasers. The PI will work to broaden the workforce in optics and photonics by training undergraduate students in research and integrating the results of this research project into the physics curriculum. Participation of underrepresented minorities in STEM will be encouraged by using existing ISU infrastructure to recruit and train underrepresented students, including outreach to local high school students.TECHNICAL SUMMARY:Resonant optical excitation of high refractive-index dielectric particles offers unique opportunities to demonstrate novel nanophotonic effects such as nonradiating anapole states, optimum forward scattering, and magnetic hotspot enhanced Purcell effects. These novel nanophotonic effects observed are related to the excitation of single dipolar modes in high-index lossless dielectric materials. These effects are inaccessible for microscale objects due to the contributions from higher order multipolar modes under plane wave illumination. Hence, observation of nanophotonic effects is currently restricted to a few relatively high-index materials in the limit of nanometer size – typically within silicon and germanium. It was recently theoretically predicted that one can unravel dipolar regimes in homogenous high-index spheres with a wide range of size parameter and refractive indices under illumination. The research team at Illinois State University (ISU) plans to experimentally unravel the dipolar regime, excite non-radiating anapole states, and demonstrate zero backscattering in mid-index (1.5 n 3.0) dielectric spheres in the micrometer range under illumination with tightly focused Gaussian beams (TFGBs). TFGBs selectively excite a few relevant Mie coefficients and control the relative weight of the different multipolar modes of the incident field. This approach will enable the investigators to unravel the dipolar regime and associated novel nanophotonic effects in microscale homogenous spheres in the mid-index regime. Understanding these phenomena opens up enormous possibilities in terms of availability of materials and objects with size parameters well beyond the current physical picture for related nanophotonic applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.