A Waveguide Made of Hot Air

Abstract

During the cold war, politicians spoke of weapon technologies that seemed to come from science fiction [1], including high-power laser beams for fighting remote battles in the sky. The ability to transmit a powerful laser beam through the atmosphere to a distant location—albeit for friendlier purposes—may become reality thanks to the latest discovery by Howard Milchberg and his colleagues at the University of Maryland in College Park. In Physical Review X, they demonstrate that a laser beam can be efficiently channeled through a gas and arrive at its destination with a much higher average power than was previously thought possible [2]. Their trick is to use a square-shaped bundle of four intense filaments of light that leave behind a trail of hot gas: The four hot air columns expand and create a central zone of higher-density air that serves as a waveguide for subsequent pulses of light. The researcher’s method could be used to direct laser energy to remote locations, providing a new way to, for instance, nudge space debris out of Earth’s orbit. Other applications include the remote detection of radioactive or hazardous materials and atmospheric laser communications.