Mirrors are used not only in daily life but also in cutting-edge technologies such as semi­conductor processing and high-resolution displays. Recently, a powerful Bragg reflection mirror based on high-index meta­materials has been developed that only reflects desired light. A research team led by Gi-Ra Yi at Pohang University of Science & Techno­logy (Postech) with the research team led by Seok Joon Kwon and Pil Jin Yoo at Sung­kyunkwan University have together developed an ultrahigh refractive index meta­material by closely packing gold nano­spheres and a reflector that combines the meta­material with a polymer.

Meta­materials – with properties that do not exist in nature – can be designed to have a negative or ultrahigh refractive index. However, meta­materials with a high refractive index still have limita­tions from designing to manufacturing. To overcome this issue, the research team developed a meta­material that is uniformly arranged with the 1-nano­meter-level gaps by assembling spherical gold nano­particles.

This material, which maximizes light-matter inter­action, recorded the highest refractive index in the visible and near-infrared regions. The 2D super­structures exhibited the highest-ever refrac­tive index of 7.8. The distributed Bragg reflector (DBR), which is made by stacking these meta­materials and polymer layers with a low refractive index, strongly reflected specific wavelengths.

Further­more, the research team established the theory of a plasmonic perco­lation model that can explain the extremely high refractive index. As it theo­retically explains the ultrahigh refractive index of metamaterials that could not be explained in previous studies, the develop­ment of related research fields is anticipated in the future. This study is also garnering attention from academic circles and industry for its applica­bility in precise semi­conductor processes and high-resolution displays. (Source: Postech)

Reference: D.-I. Shin et al.: Percolated Plasmonic Superlattices of Nanospheres with 1 nm-Level Gap as High-Index Metamaterials, Adv. Mat. 34, 2203942 (2022); DOI: 10.1002/adma.202203942

Link: Dept. of Chemical Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea