Researchers are now capable of deflecting beams of laser light by using an invisible grating system made of air. The optical system is created using ultrasound and is not damaged by the laser (it is just air, after all), and it doesn’t reduce the quality of the beam.
The team has already applied for a patent on this new approach. It consists of using a special loudspeaker to create a pattern of air at different densities. While the quality stays the same, the setup has only a 50 percent efficiency, but the team believes they can push further in the future,
“We’ve generated an optical grating with the help of acoustic density waves,” first author Yannick Schrödel, a PhD student at DESY and Helmholtz Institute Jena, said in a statement.
The work used a soundwave of 140 decibels (like standing close to a jet engine) but in the ultrasound range, so it can’t be heard by the human ear. The waves create layers with different densities. The work was inspired by how light is bent by the Earth’s atmosphere as it passes through layers of different densities.
“However, deflecting light by diffraction grating allows much more precise control of the laser light compared to deflection in the Earth's atmosphere,” explains Schrödel. “The properties of the optical grating are influenced by the frequency and intensity – in other words, the volume – of the sound waves.”
In the experiment, the researchers employed an infrared laser pulse with a peak power of 20 gigawatts. That is equivalent to about 2 billion LEDs, or the energy required to send 16.5 DeLoreans back to the future. Lasers such as this can be used to process materials and more, given their power.
“In this power range, the material properties of mirrors, lenses, and prisms significantly limit their use, and such optical elements are easily damaged by strong laser beams in practice,” added project lead Christoph Heyl, also from DESY and Helmholtz Institute Jena. “In addition, the quality of the laser beam suffers. In contrast, we’ve managed to deflect laser beams in a quality-preserving way without contact.”
The team was able to create a grating system, but they believe that other optical structures could be made out of air, such as lenses and waveguides. And, it could even be possible to use different gases to interact with different types of lasers.
“The potential of contactless control of light and its extension to other applications can currently only be imagined,” stated Heyl. “Modern optics is based almost exclusively on the interaction of light with solid matter. Our approach opens up a completely new direction.”
The study is published in Nature Photonics.