Researchers at Lawrence Livermore National Laboratory have used advanced 3D-printing to create microscale helical metamaterials. These structures manipulate terahertz (THz) radiation in powerful new ways.
By pushing past long-standing technical limits at THz frequencies, their work opens doors to next-generation communications, sensing, and imaging. There’s even potential for new forms of encrypted data encoding.
Closing the Technology Gap in the Terahertz Spectrum
The terahertz band sits between microwaves and infrared light. It’s a notoriously tricky region for technology.
THz wavelengths are too long for standard optical components. They’re also too fast for regular electronic devices, leaving a “THz gap” where useful tools are rare.
This gap has especially limited devices like waveplates, which control light polarization. Without solid THz waveplates, many advanced applications in spectroscopy and imaging just aren’t possible.
Why Polarization Control Matters at THz Frequencies
Polarization describes the orientation of an electromagnetic wave’s electric field. At THz frequencies, precise polarization control is crucial for probing subtle material properties.
This is especially true in biological and chemical systems. But until now, efficient THz components have been hard to come by.
3D-Printed Helical Metamaterials for THz Wave Control
The Lawrence Livermore team turned to two-photon polymerization, an ultra-precise 3D-printing technique. It can produce complex microscale structures.
They fabricated tiny helical metamaterials that interact strongly with THz waves. These helices were tuned for ~300‑micrometer wavelengths, which is a sweet spot for THz operation.
By matching the structure size with the target wavelength, the team boosted the helices’ ability to shape and transform THz beams. That’s some clever engineering.
First Full Parametric Study of THz Helices
The researchers ran the first comprehensive parametric analysis of THz helical metamaterials. They systematically varied key geometric parameters:
By optimizing these variables, the team engineered helices that operate as quarter waveplates. These devices convert linearly polarized THz beams into circularly polarized ones with high efficiency and broad bandwidth.
Generating Circularly Polarized THz Beams
The optimized helical metamaterials produced strong, broadband circularly polarized THz beams over wide angles. They also maintained high transmission.
This is a big deal, since circular polarization interacts with matter in a very different way than linear polarization does.
Many biological molecules and chiral materials respond selectively to circular polarization. That makes these THz waveplates powerful tools for advanced spectroscopy.
Chirality and Biomolecular Detection
Chirality—the property of being non-superimposable on a mirror image—is fundamental in chemistry and biology. Proteins, DNA, and many pharmaceuticals are chiral.
Their vibrational modes often lie in the THz range. Circularly polarized THz radiation can selectively probe these chiral vibrations, enabling:
From Single Helices to Chiral QR Codes
When the helices are arranged into ordered arrays, their interactions get even more interesting. Left- and right-handed helices can couple to enhance performance and add new functionality.
One outcome is the ability to encode information in the phase and polarization of THz waves, not just in intensity.
The World’s First Chiral QR Code
By carefully designing arrays of opposite-handed helices, the team created what they call the world’s first “chiral QR code.” This pattern can only be read using the right combination of THz frequency and circular polarization.
It’s a novel layer of physical encryption for security and authentication. Data stays invisible to conventional optical or electronic readers that lack the correct polarization and frequency.
Scaling Up with Parallel 3D Printing
Microscale 3D printing isn’t fast—making millions of tiny structures can take ages. To fix this, the researchers used a parallel 3D-printing approach with metalens arrays.
These metalenses let them print many helices at once. They could also selectively fabricate opposite-handed structures in the same process, which sped up production of complex chiral metasurfaces by a lot.
Path to Real-World THz Devices
Published in Advanced Science, this work sketches out a promising path toward scalable, practical THz components. Some of the most exciting impact areas are:
Here is the source article for this story: 3D-printed helixes show promise as THz optical materials