In the realm of molecular science and materials engineering, the concept of chirality — objects or molecules that are mirror images but not superimposable — holds profound significance. Much like how the left and right human hands are structurally similar yet non-identical, chiral entities exhibit behavior and properties that are deeply influenced by their handedness. Chirality is a cornerstone in fields spanning biology, chemistry, and nanotechnology, fundamentally influencing everything from the twisting form of DNA to the design and efficacy of pharmaceuticals. Understanding and visualizing chirality at micro and nanoscale levels remains a critical yet elusive challenge in science.

A particularly promising avenue for characterizing chiral molecules and structures is the use of circularly polarized light within the terahertz (THz) frequency range. Occupying the electromagnetic spectrum between microwaves and infrared light, terahertz waves are exceptionally sensitive to collective molecular motions and subtle twisting modes inherent in chiral materials. Traditionally, however, the use of THz spectroscopy has been limited to bulk measurements that average responses across the entire sample, obscuring spatial variations in chirality critical for nuanced material characterization and biomedical applications.

Breakthrough research led by Professor Katsuhiko Miyamoto at Chiba University, Japan, alongside collaborators at Tohoku University and the National Institute for Materials Science, has shattered this constraint. By developing an innovative imaging technique based on terahertz circular dichroism (TCD) spectroscopy combined with precisely engineered moiré metasurfaces, the team has for the first time realized direct, high-resolution two-dimensional mapping of chirality distributions. This novel approach moves beyond mere chiral signal averaging and enables the visualization of chirality’s spatial heterogeneity with unprecedented clarity.

At the core of this advancement lies the crafting of moiré metasurfaces — meticulously fabricated nanostructured assemblies consisting of stacked microscopic silver disks with controlled lateral shifts and rotations at micrometer dimensions. These engineered surfaces exhibit intricate interference patterns that manifest as alternating right-handed and left-handed chiral regions. Their carefully calibrated geometry enables strong interaction with circularly polarized THz radiation, whereby distinct local circular dichroism spectral signatures arise from the underlying chirality variations.

Illuminating these metasurfaces with circularly polarized terahertz waves, the researchers observed spatially dependent differential absorption of left- versus right-handed polarization components. By spectroscopically analyzing these signals, they generated detailed images that revealed local chiral domains, with an impressive spatial resolution on the order of 100 micrometers — approximately the width of a single human hair. This level of resolution, coupled with the ability to distinguish coexisting opposite chirality within the same sample plane, marks a transformative leap beyond conventional THz measurement techniques.

The implications of this imaging methodology extend far beyond academic curiosity. The capacity to spatially resolve chirality opens new pathways for rigorous quality control in next-generation chiral materials, which are pivotal in advanced optics, quantum devices, and chiral photonics. Furthermore, it can drive breakthroughs in biomolecular analysis by enabling visualization of protein conformations and aggregates whose chiral nuances relate directly to their biological function or pathogenicity. Crucially, the non-invasive and label-free nature of this THz circular dichroism imaging makes it an attractive tool for probing delicate biological samples or sensitive nanofabricated structures without damage.

Professor Miyamoto described the work as a response to a fundamental gap in chirality characterization—while conventional methods had only provided averaged chirality information, the true spatial arrangement had remained a mystery. “Our motivation was simple but profound: to ask not just what chirality exists, but how it is distributed. Visualizing this spatial distribution unlocks a deeper understanding of chiral phenomena,” he said. Indeed, their approach integrates optics, materials science, and nanofabrication technologies to bring this vision to fruition.

Technically, the design and fabrication of the moiré metasurface demanded precise control over the nanoscale patterning of metallic disks, ensuring the subtle offsets necessary to generate spatially alternating twisting motifs. When excited with THz circularly polarized light, these motifs selectively absorb left- or right-handed polarization components, creating differential spectral fingerprints captured by a THz spectroscopic imaging system. By scanning the beam or analyzing the reflected/transmitted signals across the metasurface, spatial maps depicting circular dichroism intensity emerge, directly correlating with localized chirality.

Looking toward the future, the research team envisions expanding this technique’s frequency range to encompass 2 to 15 THz, which would enable even finer structural analyses and broaden its applicability. This frequency scalability is expected to enhance sensitivity to diverse molecular vibrations and chiral interactions, further refining diagnostic capabilities. Potential applications span the detection of abnormal protein aggregations implicated in neurodegenerative diseases, evaluation of chiral metamaterials for Beyond 5G and upcoming 6G communication technologies, and the investigation of subtle internal distortions within quantum and soft matter systems.

The advent of this terahertz circular dichroism imaging technique thus represents a pivotal advancement in chiral science, promising to catalyze scientific and technological innovation across multiple disciplines. By translating chiral phenomena into spatially resolved, spectrally rich images, researchers can now explore the complexities of chiral matter with a precision and depth that was previously unattainable. This work not only answers longstanding questions about the spatial nature of chirality but also lays the groundwork for future breakthroughs in medicine, materials science, and telecommunications.

As the field of nanofabrication continues to evolve, producing increasingly intricate and functional chiral architectures, having a reliable, non-destructive method to image chirality at microscale resolution is indispensable. The collaborative efforts between Chiba University, Tohoku University, and the National Institute for Materials Science have thus opened a new frontier in chirality research — one that bridges optical physics and material engineering with real-world applications on the horizon.

In summary, the groundbreaking imaging of chirality through terahertz circular dichroism spectroscopy combined with moiré metasurfaces redefines the capability to study handedness in materials. By unveiling a multiscale chiral landscape where right- and left-handed domains coexist and interact, this work paves the way for innovative diagnostic tools and advanced material evaluations, heralding a future where the mysteries of chirality are not only understood but visually mapped and manipulated for technological and biomedical gains.

Subject of Research: Not applicable

Article Title: Multiscale chirality in moiré metasurfaces revealed by terahertz circular dichroism spectroscopic imaging

News Publication Date: June 2, 2026

Web References: https://www.cn.chiba-u.jp/en/news/

References:
Authors: Uina Chiba, Shota Tsuji, Gaku Oritani, Takumi Yoichi, Rinpei Sasaki, Takeo Minari, Seigo Ohno, Katsuhiko Miyamoto
Affiliations: Graduate School of Engineering, Chiba University; Research Center for Functional Materials, National Institute for Materials Science; Department of Physics, Tohoku University; Molecular Chirality Research Center, Chiba University
DOI: 10.1021/acsphotonics.6c00372

Image Credits: Professor Katsuhiko Miyamoto, Chiba University, Japan

Keywords

Chirality, Terahertz Circular Dichroism, Moiré Metasurfaces, Terahertz Imaging, Circularly Polarized Light, Nanofabrication, Chiral Metamaterials, Spectroscopic Imaging, Structural Biology, Advanced Optics, Nonlinear Optics, Quantum Materials