CAREER: Symmetry Control in Photonic Nanostructures for Enhanced Optical Properties

非技术描述：光子晶体是周期性结构的人造材料，由比原子晶体大大约一千倍的积木构成。原子晶体的对称性影响电子性质，光子晶体的对称性是决定光学性质的关键因素。然而，由于光子晶体的重复单元比原子晶体中的周期性大得多，因此可以通过使用纳米纤维技术操纵其重复单元的结构来控制光子晶体中的对称性。该CAREER奖的研究内容是对光子晶体光学特性的对称性效应进行实验和理论研究，旨在实现光学材料和光电器件的高性能。该研究与当地K-12学校和附近的美国原住民社区的纳米科学教育活动相结合，与小学教师合作。技术描述：该研究项目的主要目标是建立对光子纳米结构的光学性能如何受到结构对称性影响的具体理解。为了有效地控制点群对称性，最近开发的主要研究者的制造技术。该技术涉及硅晶片的湿法蚀刻处理。基于胶体自组装的方法以可控的方式打破平移对称性。研究了对称性对光学性质的影响：（i）薄膜有机太阳能电池的高效率，目标是超过传统理论极限的光吸收;（ii）Si基热电子红外探测器的高光响应度，目标是比当前基准更宽的带光响应度;和（iii）模仿白色甲虫鳞片中的纳米结构的人造白色涂层，其目标是在低折射率材料中具有较强光散射的较薄鳞片。基于胶体自组装的方法被开发来制造这样的结构，精确控制结构参数，以确定结构和光学散射特性之间的关系。

Non-technical Description: Photonic crystals are periodically structured artificial materials constructed from building blocks that are approximately a thousand times larger than those in atomic crystals. As symmetry in atomic crystals affects the electronic properties, symmetry in photonic crystals is a crucial factor determining the optical properties. However, because the repeating unit of photonic crystals is much larger than the periodicity in the atomic crystals, the symmetry in photonic crystals can be controlled by manipulating the structure of their repeating unit by using nanofabrication techniques. The research component of this CAREER award is to perform experimental and theoretical investigations of the symmetry effect on the optical properties of photonic crystals, aiming to achieve high performance of optical materials and optoelectronic devices. The research is integrated with nanoscience education activities at local K-12 schools and a nearby Native American community in collaboration with elementary school teachers.Technical Description: The main objective of the research project is to establish a concrete understanding of how the optical performance of photonic nanostructures is affected by the structure symmetry. For efficient control of point group symmetry, a fabrication technique recently developed by the principal investigator is employed. The technique involves wet etching processing of silicon wafers. Translational symmetry is broken in a controlled manner by methods based on colloidal self-assembly. The symmetry effect on optical properties is investigated for: (i) high efficiency in thin-film organic solar cells, targeting light absorption that surpasses the conventional theoretical limit; (ii) high photoresponsivity in Si-based hot-electron infrared detectors, targeting broader band photoresponsivity than current benchmarks; and (iii) artificial white coatings mimicking nanostructures in white beetle scales, targeting thinner scales with stronger light scattering among low-refractive-index materials. Methods based on colloidal self-assembly are developed to fabricate such structures with precise control over structural parameters to determine the relationship between the structure and the optical scattering properties.