Partial Order Colloidal Phases as Photonic Solids

非技术描述：本研究的目的是制备由非球形胶体颗粒组成的部分有序光子中间相，并表征其光学性质。这些新材料表现出晶体和玻璃之间的结构有序性，并有望强烈改变光的光谱和角传输（类似于晶体），并促进具有高各向同性的带隙（类似于玻璃）。该研究有助于澄清各种光子介质中光子带隙形成的机制，并寻求新的光学特性，如负折射的高分辨率透镜和低光速的增强非线性光学。该项目的教育活动包括：在伊萨卡科学中心开展非正式的科学学习活动;通过让代表性不足的少数群体和妇女参与研究，扩大他们对科学的参与;以及为扩大参与研究所编写的本科生研究最佳做法手册做出贡献。特别是，研究生辅导员在科学传播的公众观众，包括儿童的培训。技术说明：本项目利用形状各向异性胶体的热力学捕获光子中间相，其中有序和无序共存的一类新的光子材料，并研究其光子特性。该研究旨在了解促进显著光子特性的有序类型和界限（即，光子带隙、负折射、慢光）以及通过低成本、大面积自组装来制造用于光子板的光子中间相材料的能力。具体而言，各向异性胶体和形状二元混合物的自组织映射出楔形细胞限制下阐明稳定的光子中间相的条件。限制高度高达五层，系统密度和粒子间的相互作用是不同的，并使用定量共聚焦显微镜成像与精确的空间和时间分辨率的自组织研究。计算了模场、透射（反射）谱和态密度的空间分布，阐明了结构和光学性质的相关性。光子中间相的特征在于使用角分辨镜面反射测量探测的色散关系。通过对等势线的分析和对带隙边缘群速度的计算，分别确定了半序对折射和慢光传输特性的影响。对具有全角度负折射和有效折射率为负的光子中间相进行了点光源折射和平面透镜成像的数值模拟。

Nontechnical Description: The objective of this research project is to fabricate partial order photonic mesophases made of non-spherical colloidal particles and characterize their optical properties. These novel materials exhibit structural ordering between those of crystals and glasses and hold promise to strongly modify spectral and angular transport of light (similar to crystals) and also to promote bandgaps with high isotropy (similar to glasses). The research helps clarify the mechanisms for the formation of photonic band gaps in various photonic media and seeks novel optical properties such as negative refraction for ultrahigh resolution lenses and low speed of light for enhanced nonlinear optics. The education activities of this project include developing informal science learning activities at the Ithaca Sciencenter; broadening participation of underrepresented minorities and women in science through involving them in research; and contributing to a manual of the best practices for undergraduate research developed by the Institute for Broadening Participation. In particular, graduate student facilitators are trained in science communication to public audiences including children.Technical Description: This project exploits the thermodynamics of shape-anisotropic colloids to capture photonic mesophases, a new class of photonic materials in which order and disorder cohabit, and to study their photonic properties. The research aims to develop an understanding of the types and bounds of order that promote significant photonic properties (i.e., photonic band gaps, negative refraction, slow light) and an ability of fabricating photonic mesophase materials for photonic slabs via low-cost, large-area self-assembly. Specifically, the self-organization of anisotropic colloids and shape-binary mixtures is mapped out under wedge-cell confinement to elucidate the conditions for stabilizing photonic mesophases. Confinement height up to five layers, system density and interparticle interactions are varied and the self-organization is studied using quantitative confocal microscopy imaging with precise spatial and temporal resolution. The spatial distributions of the mode fields, transmission (reflection) spectra and density of states are calculated to elucidate the structure and optical property correlations. The photonic mesophases are characterized using angle-resolved specular reflectance measurements to probe the dispersion relations. The effects of partial order on refraction and slow-light propagation properties are determined from the analysis of equifrequency contours and the calculation of the group velocity at the band gap edges, respectively. Simulations of the refraction and the flat lens imaging of a point source are performed for photonic mesophases that exhibit all-angle negative refraction and effective refractive index of negative one.