CAREER: Symmetry Control in Photonic Nanostructures for Enhanced Optical Properties

非技术描述：光子晶体是一种周期性结构的人造材料，由大约比原子晶体大一千倍的积木组成。由于原子晶体的对称性会影响其电子性质，所以光子晶体的对称性是决定其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的周期性大得多，利用纳米加工技术可以通过操纵重复单元的结构来控制光子晶体的对称性。这一职业奖的研究部分是对对称性对光子晶体光学性质的影响进行实验和理论研究，旨在实现高性能的光学材料和光电子器件。这项研究与当地K-12学校和附近美洲原住民社区的纳米科学教育活动相结合，并与小学教师合作。技术描述：研究项目的主要目标是建立一个具体的理解，即光子纳米结构的光学性能如何受到结构对称性的影响。为了有效地控制点群对称性，采用了首席研究员最近开发的一种制造技术。这项技术涉及硅片的湿法刻蚀工艺。基于胶体自组装的方法以受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，目标光吸收超过传统的理论极限；(Ii)硅基热电子红外探测器的高光响应度，目标是比目前基准更宽的波段光响应率；(Iii)人造白色涂层模仿白色甲虫尺度的纳米结构，目标是更薄的尺度，在低折射率材料中具有更强的光散射。发展了基于胶体自组装的方法来制备这种结构，并通过精确控制结构参数来确定结构与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.