The visual effect is striking. “The plasma beam antenna looks like a lightsaber and is tunable, meaning we should be able to transmit across a broad range of frequencies,” says Prya Darshni, corresponding author of the journal article and a Ph.D. student at NC State. That lightsaber-like shaft is not merely a novelty; it is a precisely engineered structure. By firing a laser beam of a specific power and diameter, the researchers ionize a thin beam of air, creating a defined shaft of plasma known as a plasma filament. Within that filament, free electrons respond to electromagnetic fields in much the same way that electrons in a metal conductor do, allowing the column of ionized gas to radiate radio signals into space.

The importance of the achievement becomes clear when one considers how fundamental antenna length is to radio engineering. The length of an antenna controls the frequencies at which radio waves can be efficiently transmitted and received, which is why antennas for different bands come in such different sizes. Physically manipulating antenna length to sweep a desired range of frequencies can be extremely challenging in certain applications, and space exploration technologies are a prime example. Deployable booms, telescoping rods and mechanical reconfiguration mechanisms add mass, complexity and failure modes to spacecraft, where every gram of payload matters. “One of the questions we wanted to explore with this work was whether it would be possible to create plasma antennas using lasers, which would allow us to generate antennas at whatever length was needed,” Darshni explains. “And we have now shown that it is possible.”

Creating the plasma filament, however, was only half of the problem. To make the plasma antenna a practical tool, the researchers also needed a way to connect it to radio technology so that a signal could actually be transmitted. A plasma column floating in air has no wire to attach a feed line to, and touching it with metallic hardware would defeat much of the purpose of a reconfigurable, structure-free antenna. The team’s solution was to develop and demonstrate a contactless antenna-feed: a metal ring that serves as a capacitor. The laser passes through the ring, creating a plasma filament that is surrounded by the capacitor. By generating an electromagnetic field with the capacitor, the researchers can interact with the plasma beam without ever making physical contact with it.

The complete system operates in a straightforward sequence. A radio frequency generator feeds a signal into the capacitor ring; this generates the appropriate electromagnetic field around the plasma column; and that field then causes the plasma filament antenna to transmit radio waves at the appropriate frequency. In the published demonstration, the team transmitted a 30 MHz signal in the VHF band, a frequency range used for applications from FM radio broadcasting to aviation communications. The contactless coupling scheme is a critical piece of engineering in its own right, because it solves the fundamental interface problem between solid-state radio electronics and a gaseous conductor that exists only where the laser has ionized the air.

Tunability is where the concept becomes genuinely powerful. “By controlling the parameters of the laser, you can control the characteristics of the plasma filament – including its length,” says Darshni. Because antenna length dictates resonant frequency, a laser-defined filament whose length can be adjusted on the fly is effectively a broadband, continuously tunable antenna. “This is valuable for applications where you need an antenna that can sweep all frequencies,” she notes. But frequency agility is not the only degree of freedom the technique offers. “There are also applications where it is important to be able to control the angle of the antenna, in order to target the direction of radar sweeps or to improve the strength of a signal you want to pick up,” Darshni says. “The technique we’ve demonstrated here would allow users to control the angle of the plasma filament antenna via beam steering – simply shifting the direction of the laser.” In other words, pointing the antenna becomes as simple as pointing a beam of light, with no motors, gimbals or phased-array electronics required.

The long-term implications extend well beyond the laboratory bench. Satellites and space exploration technologies are one potential area of interest, because both payload mass and the ability to scan across a wide range of frequencies are important considerations for orbital systems. An antenna that materializes on demand, changes length electronically and steers by laser could dramatically reduce the mechanical complexity of communications and radar packages on future spacecraft. Crucially, the physics does not require the vacuum of space to be abandoned as a working environment. “In low earth orbit, there is sufficient air to form a plasma,” says Paul Franzon, co-author of the paper and the Cirrus Logic Distinguished Professor of Electrical and Computer Engineering at NC State. The residual atmosphere at those altitudes, thin as it is, provides enough molecules for a laser to ionize into a usable filament.

Franzon also highlights the practical appeal of the design from a systems engineering standpoint. “This is an exciting new concept that enables one to be able to have a customized antenna without complex mechanical deployment mechanisms,” he says. For missions where unfolding a large antenna structure is one of the riskiest moments of deployment, the idea of generating the radiating element out of thin air, literally, is an attractive alternative. The same properties could eventually matter on Earth as well, in scenarios where rapidly reconfigurable, steerable antennas are needed for radar, communications or spectrum management, although the researchers emphasize that the current work is an early-stage demonstration rather than a field-ready product.

The team is careful to be precise about what has and has not been shown. While the plasma filament has now been proven to transmit radio waves, the researchers have not yet demonstrated its ability to serve as an antenna that can receive signals. Even so, Darshni sees no fundamental obstacle on that front. “There’s no reason to believe it wouldn’t also work as a receiver,” she says, since the reciprocity that governs conventional antennas suggests a structure that radiates efficiently at a given frequency should also collect signals at that frequency. Establishing reception experimentally, along with improving efficiency, power handling and filament stability, now forms the roadmap ahead.

“This is the first step, but it is a big step – it is the first time anyone has ever demonstrated that plasma-filament antennas can work,” says Darshni. “Now that we’ve shown it is possible, we can begin improving its performance.” The article, “Laser-Induced-Plasma-Filament Antenna Transmitting 30 MHz VHF,” was published with co-author Arthur Dogariu of Texas A&M University and Princeton University, who assisted with measurements, and the researchers acknowledge the NC State Instrument Shop team of Chris Hewett, Byron Goode and Joe McElveen for manufacturing the experimental components. From a glowing column of ionized air to a working radio transmitter, the demonstration marks the moment plasma antennas moved from theory into demonstrated reality – and the beginning of an effort to make light-sculpted antennas a practical tool for communications on Earth and in orbit.

Subject of Research: Laser-induced plasma filament antennas for radio transmission

Article Title: Researchers successfully demonstrate first-ever plasma beam antenna

Article References: Researchers successfully demonstrate first-ever plasma beam antenna. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: plasma antenna, laser-induced plasma, plasma filament, radio transmission, VHF, beam steering, tunable antenna, contactless antenna feed, NC State University, IEEE Journal of Microwaves, space communications, photonics

For decades, engineers have faced an uncomfortable trade-off in meeting that demand. Mechanical scanning systems, built around gimbaled mirrors and rotating assemblies, can cover very large angles, but they carry the penalties of size, weight, power consumption, and moving parts that wear out and drift out of alignment. Chip-based optical phased arrays, by contrast, eliminate almost all mechanical motion by electronically controlling the phase of light emitted from many tiny antennas. Yet most phased arrays scan widely in only one direction. Extending them to true two-dimensional operation typically requires densely packed arrays and large numbers of individually controlled elements, which drives up electrical complexity, fabrication difficulty, and energy consumption. The result has been a persistent gap between what free-space optical systems need and what chip-scale technology has been able to deliver.

A research team led by Professor Juejun Hu’s group at the Massachusetts Institute of Technology, working with the Singapore-MIT Alliance for Research and Technology and collaborators, has now demonstrated a hybrid photonic platform that closes much of that gap. Reported in the journal Opto-Electronic Advances, the platform achieves two-dimensional beam steering across a measured field of view of 161 degrees while maintaining nearly diffraction-limited beam quality across a broad angular range. The work was made available online on August 23, 2026, in the Early View section of the journal, and it represents a distinctly different architectural philosophy from the phased-array mainstream.

The key insight behind the new platform comes from an unexpected direction: optical projection. Rather than controlling a dense array of optical antennas with thousands of independently tuned phase shifters, the system uses a silicon photonic integrated circuit as a light-routing engine. The circuit directs light through an on-chip network of switches to a selected output waveguide. At that output, a freeform micro-optical reflector turns the guided light upward, out of the chip plane, and shapes it into a clean free-space beam. In effect, the chip behaves like a projector that selects which of several pre-defined optical paths the light will follow, rather than an antenna array that synthesizes a direction wavefront by wavefront.

The second stage of the architecture is where the wide-angle steering happens. After leaving the reflector, the beam passes through a metasurface—a flat optical element patterned with nanoscale structures that impose precise, position-dependent changes on the light. According to Professor Hu, the position of the selected reflector determines the direction in which the metasurface sends the beam, so choosing a different optical path on the chip directly produces a different steering direction. This division of labor is the heart of the design. The photonic integrated circuit handles the discrete selection of output paths with low complexity, while the metasurface performs the heavy optical work of redirecting and correcting the beam across an ultrawide angular range.

Building the platform required weaving together several fabrication traditions that rarely meet on a single substrate. The team combined analytical optical design, numerical modeling, established semiconductor manufacturing, three-dimensional microprinting, and nanofabrication. The photonic integrated circuit itself was produced using a standard silicon photonics foundry process, meaning the light-routing backbone could in principle be manufactured with the same mature industrial tooling that produces commercial silicon photonic chips. The freeform reflectors, which must efficiently transform the guided optical mode traveling inside a waveguide into a Gaussian-like free-space beam, were designed for that conversion task and then printed directly onto the chip in three dimensions, a technique that allows curved micro-optical geometries impossible with conventional planar lithography.

The metasurface followed a similarly disciplined design pipeline. Its pattern was first established through an analytical design framework, giving the team a physically grounded starting point, and was then refined using optical simulations specifically aimed at reducing aberrations at large steering angles. Aberration control is critical here: when a beam strikes a flat optic far off its nominal axis, simple lenses and gratings tend to smear the focus and distort the wavefront. By optimizing the nanoscale pattern against these off-axis effects, the researchers ensured that beams steered toward the edges of the field of view would emerge nearly as clean as those near the center. After careful assembly and alignment of the chip, reflectors, and metasurface, the complete system was tested at telecommunications wavelengths, the near-infrared band used by fiber networks and many free-space optical links.

The measured results are what make the demonstration notable. The system steered a beam in two dimensions across a 161-degree field of view—an extraordinarily wide cone for any chip-scale device—while keeping the output nearly diffraction-limited, meaning the beam spread was close to the fundamental physical limit set by the aperture rather than degraded by optical imperfections. Because steering is achieved by switching among discrete reflector positions rather than continuously phasing an antenna array, the control electronics remain comparatively simple, avoiding the dense wiring and high power draw that plague two-dimensional phased arrays. The trade-off is that the platform steers among a set of discrete directions, but the researchers see that as a starting point rather than a ceiling.

The architecture, in fact, offers several clear paths toward even better performance. Compact piezoelectric translation could add fine or continuous steering between the discrete directions provided by the current reflector array, blending the simplicity of the switching approach with the smooth coverage of a scanner. Lower-loss photonic foundry processes, improved assembly alignment, and direction-specific metasurface optimization could each raise the overall optical efficiency, putting more of the laser’s power into the steered beam. Increasing the effective aperture, or pairing the platform with beam-expanding optics, would narrow the output beam further, which is essential for long-distance links where divergence over kilometers of free space determines whether enough light arrives at the receiver.

Professor Hu notes that these advances will build on the demonstrated wide field of view and high beam quality, moving the technology toward scalable optical projectors for communications, sensing, and other applications requiring agile, wide-angle control of light. If the hybrid approach matures along those lines, the implications reach across the free-space photonics landscape: inter-satellite optical links that steer across the sky from a chip smaller than a coin, airborne LiDAR with no moving gimbal, and point-to-point Li-Fi communication that can retarget a data beam instantly. A patent based on the technology has been filed by 2Pi Inc., signaling that the researchers see a commercial future for a platform that turns beam steering from a mechanical problem into a manufacturing one.

Subject of Research: Chip-scale hybrid photonic integrated circuit and metasurface platform for ultrawide-angle two-dimensional optical beam steering

Article Title: New chip-scale optical platform enables high-quality ultrawide beam steering

Article References: New chip-scale optical platform enables high-quality ultrawide beam steering. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: beam steering, photonics, metasurface, photonic integrated circuit, silicon photonics, free-space optics, LiDAR, optical communications, micro-optics, nanofabrication, Li-Fi, optical phased arrays

Gradient-index, or GRIN, lenses have long fascinated engineers because they bend and focus waves not through curved surfaces, as conventional optics does, but through spatially varying dielectric properties distributed throughout the volume of the material. Instead of a shaped piece of glass, a GRIN lens is essentially a structured medium whose effective refractive index changes gradually from point to point. When a wave propagates through such a medium, its wavefront is progressively reshaped, allowing the lens to collimate, focus, or steer beams with remarkable freedom. For compact beam-steering systems, particularly those needed in satellite communications, radar, and next-generation wireless networks, this kind of wavefront control in a flat or modestly sized package is extremely attractive.

The difficulty has always been the inverse problem. Forward design is straightforward: given a specified permittivity distribution, electromagnetic solvers can predict exactly how waves will behave. Inverse design asks the opposite question. Given a desired field transformation, what volumetric permittivity distribution produces it? For most practical devices, this question has been answered through voxel-by-voxel topology optimization, in which the design volume is divided into thousands or millions of tiny cells, each of which is iteratively adjusted. Every iteration demands a full-wave electromagnetic simulation, and a converged design can require thousands of such simulations. On ordinary computing hardware, this process can stretch from days into weeks, and the resulting designs are often highly resonant, meaning they perform well only in a narrow frequency band and are exquisitely sensitive to fabrication tolerances.

The Siena and Inkbit team took a fundamentally different route. Rather than optimizing an arbitrary voxel map, they restricted the search space to smooth GRIN profiles appropriate for propagation-based devices. This constraint is not a limitation but a strategic advantage. Smooth, slowly varying index profiles are exactly the regime in which geometrical optics provides an accurate and computationally cheap description of wave behavior. By optimizing the geometrical optics propagation equations directly, the researchers sidestepped the need for repeated full-wave simulations entirely. The optimization problem collapses from a monstrous high-dimensional search into a tractable one that runs in minutes on a standard computer. The physics of propagation, rather than raw computational power, does the heavy lifting.

The mathematical logic behind the approach is elegant. Geometrical optics treats waves as rays that follow paths determined by the local refractive index, and the accumulated phase along each ray dictates how the wavefront evolves. By parameterizing the permittivity distribution with a modest number of smooth basis functions, the designers created a differentiable mapping from the lens parameters to the resulting field transformation. Gradient-based optimization then adjusts those parameters until the predicted output field matches the target, whether that target is a focused spot, a collimated beam, or, in the demonstrated case, a set of independently steered beams corresponding to different feed positions. Because the optimization operates on smooth profiles, the resulting designs are inherently broadband: a gradual index variation does not suddenly stop working when the frequency shifts, unlike resonant structures tuned to a single operating point.

To prove that the method delivers real hardware rather than pretty simulations, the team fabricated a multi-feed GRIN lens using additive manufacturing. The internal architecture is based on a three-dimensional gyroid, one of the most celebrated geometries in modern materials science. A gyroid is a triply periodic minimal surface, a structure that divides space into two intertwined, self-connected labyrinths with no straight edges or flat faces. By controlling the local density and dimensions of the gyroid lattice, the effective dielectric constant of the material can be tuned continuously across the lens volume, translating the smooth permittivity profile computed by the optimizer into a physical object. Additive manufacturing is the enabling technology here, since no conventional machining process could produce such an intricate, spatially graded internal scaffold.

The experimental results are striking. The fabricated lens supports multiple feed ports, each of which launches a beam in a different direction, effectively turning a single passive structure into a multi-beam former. As the feed is switched, the beam scans continuously across a ±35-degree range, and the measured performance holds across a 33 percent fractional bandwidth, a figure that comfortably encompasses many practical communication and sensing bands. The researchers report low scan loss, meaning the beam does not weaken appreciably as it moves away from boresight, and excellent beam fidelity, meaning the radiated pattern retains its shape and sidelobe behavior across the scanning range. These are precisely the attributes that matter in real phased-array and multibeam antenna systems, where scan loss and pattern distortion have historically limited performance.

The significance of the demonstration extends beyond the specific device. Multi-beam formers are workhorses of satellite ground stations, 5G and future 6G base stations, and high-throughput communication links, where a single aperture must serve many users or satellites simultaneously. Conventional solutions rely on phased arrays with hundreds of individually controlled elements, each requiring amplifiers, phase shifters, and calibration, or on quasi-optical systems such as Rotman lenses and reflectarrays that involve their own design compromises. A passively operated GRIN lens that steers beams simply by selecting among fixed feeds offers a dramatically simpler architecture with no active electronics in the beam-forming path, reducing cost, power consumption, and failure modes.

Equally important is what the method implies for the design workflow of metamaterial devices in general. The gap between an electromagnetic specification and a printable file has been the central obstacle to scalable wavefront engineering. Topology optimization, for all its power, produces designs whose complexity is entangled with the simulation cost of producing them, and whose narrowband resonant character often clashes with real-world bandwidth requirements. By anchoring the inverse problem in geometrical optics and smooth profiles, the new framework establishes what the authors describe as a direct pathway from electromagnetic functionality to manufacturable metamaterial devices. The optimization is fast enough to be iterative in a design office, and the output is, by construction, compatible with additive manufacturing processes that can realize graded effective media.

The work was carried out within the framework of the Huawei–University of Siena Joint Laboratory, a collaboration that reflects the growing industrial appetite for beam-steering hardware as wireless systems push toward higher frequencies and denser networks. The article, authored by Ilir Gashi, Scott Twiddy, Zachary Nelson, Stefano Maci, and Matteo Albani, with Twiddy and Nelson contributing equally, was published open access on 26 September 2026. As additive manufacturing continues to mature, allowing ever finer control over graded internal architectures, the combination of physics-informed inverse design and freeform fabrication points toward a future in which antennas and lenses are no longer designed component by component but computed as a whole, with the desired electromagnetic behavior specified first and the material emerging as the answer. For a field that has spent decades choosing between the speed of approximate models and the accuracy of exhaustive simulation, a method that achieves wideband, experimentally verified performance in minutes of computation marks a genuine turning point.

Subject of Research: Inverse design of gradient-index metamaterials for wideband multi-beam forming

Article Title: Inverse design of metamaterials for wideband multi-beam former

Article References: Gashi, I., Twiddy, S., Nelson, Z., Maci, S., & Albani, M. (2026). Inverse design of metamaterials for wideband multi-beam former. Communications Engineering. https://doi.org/10.1038/s44172-026-00787-1

Image Credits: AI Generated

DOI: 10.1038/s44172-026-00787-1

Keywords: metamaterials, inverse design, gradient-index lens, beam steering, additive manufacturing, gyroid, multi-beam former, electromagnetics, geometrical optics, antenna engineering, topology optimization, wavefront engineering

The logic behind the research begins with a simple economic reality. Large geostationary communications satellites can deliver enormous capacity, but they are expensive to build and costly to launch. Small satellites, by contrast, are cheap, light, and increasingly capable, which makes it practical to fly them in constellations: hundreds or thousands of spacecraft working in concert to blanket the globe with coverage. Such constellations promise affordable high-speed connectivity for remote regions, ships at sea, aircraft in transit, and communities that terrestrial fiber infrastructure has never reached. Yet small satellites face a fundamental constraint. The volume and weight allowances on a launch vehicle are brutally limited, and conventional radio hardware, particularly the large antennas needed for high-gain directional communication, simply does not fit inside a compact spacecraft bus.

The solution pursued by the Science Tokyo team, led by Professor Hiraku Sakamoto of the Department of Mechanical Engineering, Associate Professor Atsushi Shirane of the Laboratory for Future Interdisciplinary Research of Science and Technology, and Professor Kenichi Okada of the Department of Electrical and Electronic Engineering, draws on the ancient art of origami. Foldable membrane antennas are thin, lightweight structures that can be stowed compactly during launch and then unfolded in orbit into a large radiating aperture. The concept is elegant on paper: the satellite gains a big antenna without carrying a big antenna through the atmosphere. But elegance collides with physics the moment the membrane deploys. Thin flexible structures do not spring into a perfectly planar shape. They warp, bend, and ripple, and those small geometric deviations have outsized consequences for a phased-array system.

A phased-array transceiver works by coordinating many individual radiating elements so that their signals combine constructively in one direction and destructively in all others, steering a focused beam electronically without any moving parts. The technique depends on exquisite synchronization: the relative timing and phase of each element’s signal must correspond precisely to the physical positions of the elements. When a membrane antenna deploys with even small non-planar deformations, the actual spacing between elements no longer matches the assumed geometry. The beam pattern degrades, sidelobes grow, and the carefully engineered directional performance collapses. This deformation problem has been the central barrier preventing foldable membrane arrays from graduating from laboratory curiosities to operational satellite hardware.

The Science Tokyo team’s breakthrough was to build a transmitter that measures and compensates for its own deformation. Their Ka-band, 16-element active phased-array transmitter was mounted across two separate boards on a deployable membrane and carried aboard the RAISE-4 small satellite, which launched on December 14, 2025 as part of the HELIOS-R project within JAXA’s Innovative Satellite Technology Demonstration-4 program. After the membrane unfolded in orbit, the system applied a calibration method previously validated in ground testing to estimate the actual bend between its two boards. With that estimate in hand, the transceiver electronically adjusted the signal timing of each antenna element, restoring the coherent coordination that the warped geometry would otherwise have destroyed.

The in-orbit experiments, which began on March 13, 2026, delivered unambiguous results. Directional beam control operated correctly both independently on each transmitter board and simultaneously across both, and the calibration scheme successfully compensated for the membrane’s non-planar shape after deployment. In practical terms, the satellite demonstrated that a folded, flexible, imperfectly deployed antenna could still deliver the precise electronic beam steering that modern satellite communications demand. The team also examined how transmitter temperature affected communication performance, gathering flight data that will inform the design of future systems expected to endure the thermal swings of the space environment, where surfaces cycle between intense sunlight and frigid eclipse every orbit.

The significance of the demonstration extends well beyond a single successful experiment. By showing that a high-performance phased-array transceiver can be reliably packaged inside a small satellite, the work establishes a foundation for scaling up to larger deployable arrays. Larger apertures mean higher gain, stronger links, and greater data throughput, which are exactly the qualities next-generation satellite networks require. The architecture validated on RAISE-4 suggests a path by which constellations of modest, inexpensive spacecraft could collectively deliver the kind of capacity and coverage traditionally reserved for their giant, costly counterparts, bringing genuinely global broadband coverage a step closer to reality and promising better connectivity for underserved regions that have waited decades for it.

Sakamoto and his colleagues see the work as a catalyst for the coming generation of wireless infrastructure. “We expect our results to accelerate the adoption of satellite constellation-based wireless communication systems in the 6G era, helping realize a society in which anyone can connect anytime and anywhere,” Sakamoto said. The statement captures the broader vision driving the field: a future in which the boundary between terrestrial and space communications dissolves, and connectivity follows people rather than the other way around. Direct-to-device services, resilient disaster communications, and ubiquitous broadband all depend on the kind of compact, deployable, electronically steered antenna technology that this demonstration has now proven in the harshest test environment available: space itself.

The project also carried a human dimension that the researchers regard as central to its legacy. More than 20 students from Science Tokyo participated in the development of the space-demonstration system, gaining hands-on experience in every stage of designing, building, and operating flight hardware. “The project therefore contributes not only to technological advancement but also to the education and training of future professionals in the increasingly important fields of space technology and wireless communications,” Sakamoto concluded. As the space economy expands and the demand for satellite communications expertise intensifies, that pipeline of trained engineers may prove as consequential as the technology itself.

From origami-inspired membranes to self-calibrating electronics, the RAISE-4 experiment weaves together mechanical engineering, radio-frequency design, and orbital operations into a single working system. The research, published in the IEEE International MTT Symposia under the title “On-Orbit Demonstration of a Deployable Ka-Band 16-Element Active Phased-Array Transmitter,” marks the moment deployable phased-array technology moved from promise to proof. If the vision holds, the satellites that carry humanity’s 6G traffic may well unfold in orbit like paper sculptures, quietly bending to the realities of space while keeping their beams locked on the users below.

Subject of Research: In-orbit demonstration of a deployable Ka-band phased-array transceiver with non-planar deformation correction for small satellite communications

Article Title: Wireless communications breakthrough: a deployable phased-array transceiver for small satellites

Article References: Wireless communications breakthrough: a deployable phased-array transceiver for small satellites. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: small satellites, phased-array transceiver, deployable membrane antenna, origami antenna, 6G, Beyond 5G, satellite constellations, RAISE-4, JAXA, Ka-band, beam steering, Science Tokyo

A new analysis published in Communications Engineering examines how two familiar wave phenomena, reflection and transmission, can be harnessed systematically to keep terahertz links alive when the direct path between transmitter and receiver is blocked. The work argues that non-line-of-sight terahertz communication should not be treated as an afterthought or a failure mode, but as a first-class design objective, engineered deliberately into the architecture of future sixth-generation networks. By treating reflective surfaces such as walls, ceilings, glass facades, and even road signs as passive allies, and by exploiting controlled transmission through materials such as drywall and window glass, the study sketches a pathway toward terahertz coverage that survives the shadows cast by everyday obstacles.

The scale of the challenge is rooted in fundamental electromagnetics. As frequency increases, the free-space path loss between two antennas grows with the square of the frequency, so a terahertz link at 300 gigahertz suffers dramatically more spreading loss than a microwave link carrying the same distance. Diffraction, the phenomenon that allows lower-frequency radio waves to bend around corners and fill rooms with coverage, becomes vanishingly weak at terahertz frequencies because the wavelengths, on the order of a millimeter or less, are tiny compared with the edges and gaps of ordinary objects. Scattering from rough surfaces, which would smear energy in many directions at lower frequencies, becomes more specular and directional, meaning that a terahertz wave bounces off a flat wall much the way a billiard ball bounces off a cushion: predictably, but only along a narrow geometric path determined by the law of reflection.

This directional character is a double-edged sword. On one hand, it means that a blocked terahertz link cannot rely on the diffuse, multipath-rich propagation that made older cellular systems robust. On the other hand, it means that reflected paths are stable, identifiable, and potentially very high quality. A signal that bounces once off a well-positioned wall arrives with a predictable delay, a predictable angle of arrival, and, if the surface is sufficiently smooth and conductive, only a modest additional loss. The new analysis emphasizes that in many indoor and street-canyon scenarios, first- and second-order reflected paths can deliver received power levels well within the sensitivity range of modern terahertz receivers, provided that the antenna beams are steered to illuminate and collect from those paths deliberately.

Beam steering is therefore the linchpin of the approach. Terahertz systems almost universally employ highly directional antennas, often implemented as phased arrays of many small radiating elements, to concentrate their limited power into a narrow pencil beam and to overcome path loss. In a line-of-sight world, pointing such a beam is straightforward. In a non-line-of-sight world, the network must first discover which reflective or transmissive paths exist, then select the best one, and then keep the beam locked onto it as people move and doors swing open. The analysis highlights beam management as a central research problem: hierarchical search procedures, machine-learning-assisted path prediction, and the use of out-of-band or sub-6-gigahertz control channels to cue the terahertz beam are all candidate techniques for finding a viable reflected route in milliseconds rather than seconds.

Reconfigurable intelligent surfaces, sometimes called smart metasurfaces, extend this idea from accidental reflectors to engineered ones. These are thin panels studded with subwavelength elements whose electromagnetic response can be tuned electronically, allowing the panel to act as a programmable mirror that redirects an incoming terahertz beam toward a chosen receiver, or even to shape the wavefront in ways a plain wall never could. Mounted on ceilings, building facades, or interior walls, such surfaces could serve as deliberate relay points, stitching together coverage in courtyards, corridors, and factory floors where no natural reflection geometry happens to work. The study situates these engineered surfaces alongside natural reflections as complementary tools in the non-line-of-sight toolkit, noting that their low power consumption and passive operating principle make them attractive for dense deployment.

Transmission, the second pillar of the analysis, is often dismissed at terahertz frequencies because many common building materials attenuate the signal severely. Concrete and brick are effectively opaque, and even wood and glass introduce losses that grow rapidly with frequency and thickness. Yet the picture is nuanced. Drywall, plasterboard, and standard window glass can pass usable fractions of the incident power at the lower end of the terahertz range, particularly near 100 to 140 gigahertz, where several standards bodies are now defining early commercial allocations. A signal that passes through a single interior wall may arrive attenuated but decodable, especially when the transmitter can boost power or the receiver can integrate over longer symbol durations. The analysis argues that material-aware network planning, in which the propagation database records not only reflectivity but also transmissivity of the surfaces in a given environment, allows the network to choose intelligently between penetrating an obstacle and bouncing around it.

The interplay between reflection and transmission also shapes how channel models must evolve. Classical statistical channel models, built for scattering-rich microwave environments, poorly describe terahertz links, which are dominated by a small number of deterministic geometric paths. Ray-tracing simulations, seeded with accurate three-dimensional models of buildings and streets and with measured material parameters, emerge as the preferred planning tool. The analysis stresses that measurement campaigns at terahertz frequencies remain comparatively sparse, and that closing this gap between modeled and measured channel behavior is essential before operators can trust simulated coverage maps. Hybrid approaches that combine sparse measurements with ray-tracing interpolation, updated in real time from the feedback that connected devices report, offer a pragmatic middle path.

The implications reach well beyond faster smartphone downloads. Terahertz non-line-of-sight techniques are critical for industrial wireless networks, where metal machinery guarantees that direct paths will be blocked, and where deterministic, ultra-reliable low-latency communication is a hard requirement for replacing factory cabling. They matter for vehicular networks, where the geometry of a street canyon creates rich reflection opportunities off building walls and parked vehicles, and for integrated sensing and communication, in which the same reflected terahertz signals that carry data can simultaneously image the environment. They also underpin the vision of wireless data centers and chip-to-chip links, where racks and heat sinks create a maze of reflective metal surfaces that a well-designed terahertz system can exploit rather than suffer.

Considerable engineering hurdles remain before reflected and transmitted terahertz paths can be managed at network scale. Phased arrays with thousands of elements consume significant power, and the phase shifters and amplifiers behind them are still costly at these frequencies. Beam alignment protocols must become faster and more energy-efficient, and handover between line-of-sight and non-line-of-sight states must be seamless enough that users never notice the network quietly rerouting their connection around a passing pedestrian. Standardization bodies are actively working to define the measurement, signaling, and beam-management procedures that would let multiple vendors implement interoperable non-line-of-sight behavior. What the new analysis makes clear is that the physics need not be an enemy. The same specular, mirror-like behavior that makes terahertz waves unforgiving also makes them predictable, and predictability is precisely what a carefully engineered network needs. If future 6G systems learn to treat every wall and window as potential infrastructure, the terahertz frontier may arrive not despite the obstacles in its path, but because the network has learned to use them.

Subject of Research: Non-line-of-sight terahertz communications using reflection and transmission for future 6G networks

Article Title: Non-line-of-sight terahertz communications enabled by reflection and transmission

Article References: Liu, F., Seddon, J., Belio-Apaolaza, I., G. Huggard, P., Wang, H., Lia, E., Deborgies, F., Wu, J. E., Munshi, M. N., Fice, M., & Seeds, A. (2026). Non-line-of-sight terahertz communications enabled by reflection and transmission. Communications Engineering. https://doi.org/10.1038/s44172-026-00782-6

Image Credits: AI Generated

DOI: 10.1038/s44172-026-00782-6

Keywords: terahertz communications, non-line-of-sight, 6G, beam steering, reconfigurable intelligent surfaces, reflection, transmission, channel modeling, millimeter wave, wireless networks, Communications Engineering, phased arrays