Fresnel diffraction imaging of surface nanostructure using coherent resonant X-ray scattering
Authors:
L. Burgard,
C. Neupane,
A. Balodhi,
S. Bista,
S. Butun,
R. Jangid,
A. Barbour,
N. Basit,
D. F. Agterberg,
M. Weinert,
C. Mazzoli,
M. G. Kim
Abstract:
We investigated surface nanostructures on an antiferromagnet MnBi$_2$Te$_4$ using a novel imaging technique, direct (real)-space and real time coherent X-ray imaging (direct-CXI). This technique has provided new insights into antiferromagnetic textures, including the formation of anti-phase antiferromagnetic (AFM) domains and thermal dynamics of AFM domains and domain walls. While this method prod…
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We investigated surface nanostructures on an antiferromagnet MnBi$_2$Te$_4$ using a novel imaging technique, direct (real)-space and real time coherent X-ray imaging (direct-CXI). This technique has provided new insights into antiferromagnetic textures, including the formation of anti-phase antiferromagnetic (AFM) domains and thermal dynamics of AFM domains and domain walls. While this method produces real-space images of AFM textures without requiring a complex imaging retrieval process, its underlying imaging mechanism has not been fully understood, limiting a deep understanding of AFM textures and the information they contain. By investigating the well-defined structural characteristics of the nanostructures fabricated on MnBi$_2$Te$_4$, we elucidate the imaging principle of this novel technique. We find that the observed images can be well explained by Fresnel diffraction integral. Using a simple model from classical optics, our calculations successfully reproduce the experimentally observed images of the nanostructures. This demonstrates that direct-CXI not only provides straightforward real-space imaging but also contains phase information through its Fresnel diffraction integral.
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Submitted 18 August, 2026;
originally announced August 2026.
Visible-frequency metasurfaces for broadband anomalous reflection and high-efficiency spectrum splitting
Authors:
Zhongyang Li,
Edgar Palacios,
Serkan Butun,
Koray Aydin
Abstract:
Ultrathin metasurfaces have recently emerged as promising materials to enable novel, flat optical components and surface-confined, miniature photonic devices. However, experimental realization of high-performance metasurfaces at visible frequencies has been a significant challenge due to high plasmonic losses and difficulties in high-uniformity nanofabrication. Here, we propose a highly-efficient…
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Ultrathin metasurfaces have recently emerged as promising materials to enable novel, flat optical components and surface-confined, miniature photonic devices. However, experimental realization of high-performance metasurfaces at visible frequencies has been a significant challenge due to high plasmonic losses and difficulties in high-uniformity nanofabrication. Here, we propose a highly-efficient yet simple metasurface design comprising of single gradient antenna as unit cell. We demonstrate visible broadband (450 - 850 nm) anomalous reflection and spectrum splitting with 85% conversion efficiency. Average power ratio of anomalous reflection to the strongest diffraction was calculated to be ~ 103 and measured to be ~ 10. The anomalous reflected photons and spectrum splitting performance have been visualized using CCD and characterized using angle-resolved measurement setup. Metasurface design proposed here is a clear departure from conventional metasurfaces utilizing multiple, anisotropic resonators, and could enable high-efficiency, broadband metasurfaces for achieving directional emitters, polarization/spectrum splitting surfaces for spectroscopy and photovoltaics.
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Submitted 28 October, 2014;
originally announced October 2014.