Photo Credit: Prya Darshni.
Scientific Frontline: Extended "At a Glance" Summary: Laser-Induced Plasma Beam Antenna
The Core Concept: A laser-induced plasma beam antenna is a customizable, tunable device that transmits radio waves by using a directed laser to ionize air into a thin shaft of plasma.
Key Distinction/Mechanism: Unlike traditional solid metal antennas, this system utilizes a dynamic plasma filament whose length and transmission angle can be instantly modified by adjusting the laser's power, diameter, and direction. It avoids physical distortion by employing a contactless, capacitively coupled feed ring to generate an electromagnetic field that transfers the radio frequency signal into the plasma.
Major Frameworks/Components:
- Laser-induced plasma filamentation (LIPF) to create the conductive shaft.
- A capacitively coupled, contactless metal ring acting as an antenna feed.
- A radio frequency (RF) generator to supply the high-frequency and very high-frequency (HF/VHF) signals.
- Beam steering via laser manipulation for directional control.
Branch of Science: Electrical Engineering, Plasma Physics, and Aerospace Engineering.
Future Application: The technology is highly promising for satellites and space exploration equipment in low Earth orbit, where mechanical antenna deployment is challenging but sufficient air exists to form plasma. It also offers advanced targeting capabilities for radar sweeps.
Why It Matters: By removing the need for complex mechanical deployment mechanisms, this innovation allows a single device to efficiently transmit across a broad range of frequencies and directions without moving physical parts.
Researchers have demonstrated a technique that uses a laser to produce a plasma beam antenna capable of transmitting radio waves.
“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 a journal article on the work and a PhD student at North Carolina State University. “And while we have not demonstrated its ability to serve as an antenna that can receive radio signals, there’s no reason to believe it wouldn’t also work as a receiver.”
“This is an exciting new concept that enables one to have a customized antenna without complex mechanical deployment mechanisms,” says Paul Franzon, coauthor of the paper and the Cirrus Logic Distinguished Professor of Electrical and Computer Engineering at NC State.
The length of an antenna is important because it controls the frequencies at which radio waves can be transmitted and received. However, manipulating the length of antennas to sweep a desired range of frequencies can be challenging in some applications—such as space exploration technologies.
“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,” says Darshni. “And we have now shown that it is possible.”
By firing a laser beam of a specific power and diameter, the researchers can ionize a thin beam of air, creating a defined shaft of plasma called a plasma filament.
To make the plasma antenna a practical tool, however, the researchers also needed to develop a way to connect the antenna to radio technology to transmit a radio signal.
To solve that problem, the researchers also created and demonstrated a contactless antenna feed, which consists of 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 touching it.
Altogether, the process works like this: a radio-frequency generator feeds a signal into the capacitor, which generates the appropriate electromagnetic field and causes the plasma filament antenna to transmit radio waves at the appropriate frequency.
“By controlling the parameters of the laser, you can control the characteristics of the plasma filament—including its length,” says Darshni. “This is valuable for applications where you need an antenna that can sweep all frequencies. But there’s another benefit as well.
“There are also applications where it is important to be able to control the angle of the antenna to target the direction of radar sweeps, or to improve the strength of a signal you want to pick up,” says Darshni. “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 the long term, the technology holds promise for use in a variety of applications. Satellites and space exploration technologies are one potential area of interest because payload and the ability to scan across a wide range of frequencies are both important considerations.
“In low Earth orbit, there is sufficient air to form a plasma,” says Franzon.
“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.”
Published in journal: IEEE Journal of Microwaves
Title: Laser-Induced-Plasma-Filament Antenna Transmitting 30 MHz VHF
Authors: Prya Darshni, Arthur Dogariu, and Paul D. Franzon
Source/Credit: North Carolina State University | Matt Shipman
Edited by: Scientific Frontline
Reference Number: eng100526_01