Helices Provide Terahertz Control
The terahertz (THz) frequency of the electromagnetic spectrum is the backbone of 5G and 6G telecommunications and is of great interest for medical diagnostics, security screening, and chemical sensing. An obstacle to developing THz-based technology is that the waves are too high frequency for conventional electronics and too long for many standard optical components. Lawrence Livermore scientists have created tiny 3D-printed helical structures to control THz light and overcome this impediment.
In an article published in the October 13, 2025, issue of Advanced Science, the Livermore team describes fabricating microscale helices that act as quarter-wave plates, converting light into circularly polarized beams with a right- or left-handed twist. Polarization control is crucial in modern optics, and circularly polarized light is particularly important for biomolecular sensing, as some THz vibrational modes are associated with molecular structures. The orientation matters because many biological molecules, including DNA, are also chiral. “One of the most intuitive and powerful approaches to inducing chirality is to create a helix,” says Livermore scientist Wonjin Choi, the paper’s lead author. “We optimized these parameters through simulations and then precisely 3D-printed the helix structures to achieve the desired functionality.”
Using two-photon polymerization—an ultrahigh-resolution light-based 3D-printing technique—the team tuned the helices’ shape, size, and turns to produce strong broadband THz performance. Left- and right-handed helices were arranged in patterned arrays to create the first “chiral QR code,” storing data in the polarization state of THz light. Promising applications include secure scanning in healthcare, banking, and defense.
Contact: Wonjin Choi (925) 422-9465 (choi21 [at] llnl.gov (choi21[at]llnl[dot]gov)).
Characterizing Gold under Pressure
When elements are placed under extremely high pressures, similar to those within the cores of giant planets, their atoms can rearrange in unexpected ways. Understanding material behavior under these extreme conditions (millions of times Earth’s atmospheric pressure) yields valuable insight for planetary modeling and fusion research. In a paper published in Physical Review Letters on October 27, 2025, Livermore researchers and collaborators described the highest-pressure structural measurement yet achieved in gold, helping to resolve historical discrepancies between theory and experiments.
For the study, solid gold samples were subjected to high-energy laser pulses at Livermore’s National Ignition Facility and the University of Rochester’s OMEGA EP laser system, rapidly squeezing the gold to pressures above 10 terapascals. The team used ultrafast x-ray diffraction techniques to capture atomic-scale structural changes on nanosecond timescales during the high-pressure state. The experiments revealed that gold maintains its usual face-centered cubic phase at much higher pressures than predicted, transitioning to a body-centered cubic (BCC) structure at the highest pressures measured, and surprisingly, coexisting in both states for a time when the BCC is first observed.
Since gold is a standard reference material for calibrating static-pressure measurements, researchers must understand its behavior across all structural phases to retain experimental integrity. “These experiments uncover the atomic rearrangements that occur at some of the most extreme pressures achievable in a laboratory,” says Livermore scientist and lead author Amy Coleman. “Knowing precisely how gold behaves ensures that every other experiment using it as a calibrant, from studying planetary cores to designing new materials, is grounded in a robust and validated understanding of gold’s behavior.”
Contact: Amy Coleman (925) 422-3761 (coleman55 [at] llnl.gov (coleman55[at]llnl[dot]gov)).
Alternative Planetary Water Source
When investigating whether exoplanets have the right “ingredients” to support life, researchers look for the presence of water as a key indicator. Scientists modeling the characteristics of sub-Neptune exoplanets—those that have radii 2 to 4 times larger than Earth—have concluded that some are “wet” despite their close-in orbit to their stars. For this water to exist, conventional wisdom suggests that the planets either formed farther out in the solar system and migrated inward or were impacted by icy space rocks. However, in new research published in the October 29, 2025, issue of Nature, Livermore researcher Harrison Horn and colleagues explain a novel pathway by which planets can produce their own water.
Using a laser-heated diamond-anvil cell to recreate the extreme temperature and pressure conditions at the boundary between a sub-Neptune’s hydrogen atmosphere and magma core, the researchers demonstrated that molten silicate can react with hydrogen to release oxygen, which then reacts with hydrogen to produce water. “Our experiments are the first to study these interactions at these conditions,” says Horn. “We’ve shown that water does not need to come from farther out in the solar system or be delivered by meteorite; it can be produced within a planet itself.”
The quantity of water created depends on the conditions and composition of each sub-Neptune. However, the findings suggest that even sub-Neptunes that are considered dry could become wet via this process. The results have significant implications for planetary formation and migration theories, as well as the search for life beyond Earth.
Contact: Harrison Horn (925) 422-0438 (horn24 [at] llnl.gov (horn24[at]llnl[dot]gov)).
