微小な変位が光学特性を巨大に変化させる(Tiny displacements, giant changes in optical properties)

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2024-05-16 ワシントン大学セントルイス校

ワシントン大学のロハン・ミシュラと南カリフォルニア大学のジェイカンス・ラヴィチャンドランが率いる研究チームは、結晶内のわずかな構造的無秩序が有用な光学特性に大きな影響を与えることを発見しました。彼らの研究では、結晶の原子構造における数ピコメートルの微小なずれが、ある方向では光学特性に最小限の影響を与える一方、別の角度から見ると大きな機能的向上をもたらすことが示されました。これにより、低照度条件下での赤外線イメージングの改善など、医療や自動運転車の夜間性能向上に応用できる可能性があります。

<関連情報>

ピコスケールの原子変位による屈折率の巨大変調 Giant Modulation of Refractive Index from Picoscale Atomic Displacements

Boyang Zhao, Guodong Ren, Hongyan Mei, Vincent C. Wu, Shantanu Singh, Gwan Yeong Jung, Huandong Chen, Raynald Giovine, Shanyuan Niu, Arashdeep S. Thind, Jad Salman …
Advanced Materials  Published: 23 March 2024
DOI:https://doi.org/10.1002/adma.202311559

微小な変位が光学特性を巨大に変化させる(Tiny displacements, giant changes in optical properties)

Abstract

It is shown that structural disorder—in the form of anisotropic, picoscale atomic displacements—modulates the refractive index tensor and results in the giant optical anisotropy observed in BaTiS3, a quasi-1D hexagonal chalcogenide. Single-crystal X-ray diffraction studies reveal the presence of antipolar displacements of Ti atoms within adjacent TiS6 chains along the c-axis, and threefold degenerate Ti displacements in the ab plane. 47/49Ti solid-state NMR provides additional evidence for those Ti displacements in the form of a three-horned NMR lineshape resulting from a low symmetry local environment around Ti atoms. Scanning transmission electron microscopy is used to directly observe the globally disordered Ti a–b plane displacements and find them to be ordered locally over a few unit cells. First-principles calculations show that the Ti ab plane displacements selectively reduce the refractive index along the ab-plane, while having minimal impact on the refractive index along the chain direction, thus resulting in a giant enhancement in the optical anisotropy. By showing a strong connection between structural disorder with picoscale displacements and the optical response in BaTiS3, this study opens a pathway for designing optical materials with high refractive index and functionalities such as large optical anisotropy and nonlinearity.

1700応用理学一般
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