2023-11-27 09:45:58
A new and revolutionary technique allows changing the direction of a laser beam in the air with the help of the air itself manipulated by sound waves.
The achievement is the work of a team led by Yannick Schroedel, from the German Electron Synchrotron (DESY, for its acronym in German).
Through an appropriate configuration of the sounds emitted into the air, it can behave as a set of optical parts capable of deflecting the laser beam in the desired way, with several advantages, among them that these “pieces” do not need to be repaired for damage caused. by laser rays, and that, due to their peculiar nature, such pieces preserve the original quality of the beam.
Using special speakers, the researchers shape a pattern of dense and less dense areas in the air. Similar to how differential air densities bend light in Earth’s atmosphere, the density pattern takes on the role of an optical grating that changes the direction of the laser beam.
In early laboratory tests, a strong infrared laser pulse could be redirected in this way with an efficiency of 50 percent. According to numerical models, much higher efficiencies should be possible in the future.
For the first test, the scientists had to turn up the volume of their special speakers very much. “We work at a sound level of about 140 decibels, which corresponds to a jet engine a few meters away,” explains Christoph Heyl, from DESY and the Helmholtz Institute in Jena, Germany, a member of the research team. “Fortunately, we work in the ultrasound range, which our ears don’t pick up.”
When the laser beam enters the area of influence of a speaker-reflector system, the action of sound in the air achieves the same effect as that generated by a set of solid optical components capable of deflecting the beam, and that is what happens despite there being no contact with any solid. (Image: Science Communication Lab for DESY)
The team sees great potential for high-performance optics in this technique. In their experiments, the researchers used an infrared laser pulse with a peak power of 20 gigawatts, which corresponds to the power of about two billion LED light bulbs. Lasers in this power range and above are used, for example, for materials processing, in nuclear fusion research or in more modern particle accelerators. When the power is so high, the properties of the materials of mirrors, lenses and prisms considerably limit their use, and in practice these optical elements are easily damaged by these strong laser beams. Furthermore, the quality of the laser beam suffers. “On the contrary, we have managed to deflect the laser beams without contact and preserving their quality,” explains Heyl.
Heyl, Schroedel and their colleagues present the technical details of the new laser beam control system in the academic journal Nature Photonics, under the title “Acousto-optic modulation of gigawatt-scale laser pulses in ambient air.” (Source: NCYT from Amazings)
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