This article dives into a breakthrough in terahertz (THz) photonics: optimized, 3D‑printed helical structures that act as advanced optical components at THz frequencies. Developed at Lawrence Livermore National Laboratory, these tiny helices generate circularly polarized THz beams and open the door to new devices—like the world’s first “chiral QR code” for secure data encoding.
3D‑Printed Helical Structures for Terahertz Photonics
Terahertz radiation, usually in the 0.1–10 THz range, sits between microwaves and infrared light. It’s central to emerging 5G/6G telecommunications and enables powerful imaging, sensing, and security tools.
Because it’s non‑ionizing, THz radiation is safer than X‑rays for many uses. But the THz band has always struggled with a lack of compact, robust optical components that control polarization precisely.
Devices like quarter waveplates are common in visible and infrared optics, but they’ve been tough to make for THz wavelengths. The challenges come down to size, fabrication limits, and tricky material choices.
Why Helical Designs Matter at THz Wavelengths
The Lawrence Livermore team turned to helical microstructures because helices naturally have chirality—a handedness that interacts differently with left‑ and right‑circularly polarized light. At THz wavelengths of about 300 microns, these carefully designed helices can act as compact, controllable polarization elements.
By tweaking the helix geometry, researchers can control how THz waves move and convert linear polarization into circular polarization. This finally fills a big technological gap: it lets us generate circularly polarized THz beams with structures that are both tiny and precisely engineered.
Ultrahigh‑Resolution 3D Printing: Two‑Photon Polymerization
To build these complex shapes, the researchers used two‑photon polymerization, a 3D printing technique with ultrahigh resolution. This method fires tightly focused femtosecond laser pulses into a photosensitive resin, “writing” 3D structures voxel by voxel.
It’s a great fit for THz optics. You get sub‑micron precision and the freedom to create shapes that traditional machining or lithography just can’t handle—especially at the 300‑micron wavelength scale.
Parametric Optimization of Helical Geometries
The team ran what they call the first full parametric analysis of THz helical structures. They systematically changed key design parameters to optimize performance.
By exploring these variables, the team found geometries that create strong, broadband circular polarization under a wide range of conditions.
Broadband Circular Polarization and Array Effects
The optimized helices generate circularly polarized THz beams with solid performance across a broad frequency range. They hold onto circular polarization at nearly any azimuthal angle, so the helix works no matter how it’s rotated around the beam axis.
Each helix produces either left‑ or right‑handed circular polarization, depending on its structure. When you arrange helices in arrays, they start to interact, which boosts their optical effects and points toward scalable, integrated THz components.
From Single Helices to the First “Chiral QR Code”
This interplay between geometry and polarization sparked a new idea: the chiral QR code. Instead of encoding information just through brightness or spatial pattern, this QR code hides data in the polarization phase of the THz field.
Since the information lives in the polarization state, you can only read the chiral QR code with the right THz frequency and polarization filter. That adds a tough physical encryption layer to the familiar QR code, with some real potential for secure identification, anti‑counterfeiting, and protected data tags.
Future Applications Across Technology and Science
These 3D‑printed helical THz components could do much more than just secure encoding. Chirality pops up everywhere in chemistry and biology—lots of molecules come in left‑ and right‑handed versions.
Circularly polarized THz light interacts differently with these enantiomers. That opens the door to chiral molecular sensing and new ways to detect chemicals and biological stuff.
Optimized helical structures and their arrays might drive the next wave of THz devices for all sorts of things:
Fabrication techniques like two‑photon polymerization keep getting better. Maybe these helical designs will end up as go-to building blocks for THz optics—linking the deep science of photonics with real-world systems in medicine, astronomy, security, and, well, who knows what else.
Here is the source article for this story: 3D-Printed Helixes Show Promise as THz Optical Materials