Aerial “waveguides” can help with remote sensing as well as laser beam weapons
Tube laser beams can create as many as fiber optic cables made of thin air researchers report in a study published in Physical Review X.
Laser-heated air can efficiently transmit light signals without the need to lay fiber optic cables. These airborne “waveguides” could also provide paths for ultra-high-energy lasers, which themselves do not propagate well in air, building on previous efforts touted as a way to laser beam weapons.
According to physicist Howard Milchberg of the University of Maryland in College Park, the latest experiments surpassed his team’s previous attempts with the waveguide by a factor of more than 60, increasing the length of the waveguide to nearly 50 meters.
The researchers fired the laser in “doughnut mode,” where the beam has a hollowed-out core along its length that resembles a stack of glowing donuts. The jet creates a hot, tubular layer of air wrapped around cooler, denser air. This creates something similar to a fiber-optic cable made of air: instead of a clear core covered by a plastic sheath that guides the light in conventional fiber optics, dense air acts as the core, while the hot air around it serves as the sheath.
Increasing the length of the waveguide to kilometers, according to Milchberg, consists primarily in increasing the power of the laser in the bagel mode. “The only problem is that we don’t have the kilometer” to safely shoot the laser that far, he says. An agreement with one of the US national laboratories may be needed to find a place to conduct a longer version of the experiment.
Despite the potential military applications, Milchberg says he and his team are more focused on scientific applications, such as expanding the range of systems that detect the chemical makeup of materials by shooting lasers at them and measuring the light they emit. Air-borne waveguides can send the emitted light back to distant systems, instead of coming up close to analyze the sample.
