Lasers are now part of our daily lives, be it in communications, manufacturing, medicine, defense, audiovisual media, astronomy and many other areas of scientific research. But all of these scenarios, as varied and varied as they are, have one thing in common: there are only a very limited number of ways to deflect the flow of photons.
The most obvious way is to take advantage of it reflective properties a material such as aluminum or silver used in mirror coatings. Alternatively, we can also rely on them refraction. When wavy light passes through another transparent medium with different properties (more precisely, a different refractive index), the wave front is deflected. For this reason, for example, a laser beam changes direction when it penetrates water or a more or less dense layer of the atmosphere.
An example of the refraction of laser beams when changing media. © Iowa College of Liberal Arts and Sciences Resource Center
An example of the refraction of laser beams when changing media. © Iowa College of Liberal Arts and Sciences Resource CenterThere are other, more subtle ways to achieve this. But everywhere, Almost all of these approaches are based on the interaction of photons with another material with very specific properties. This works perfectly in the vast majority of cases. But there are more and more exceptions.
Over the past few decades, the power of lasers used in cutting-edge scientific research has increased exponentially. Professionals who work with these powerful beams are beginning to realize a major problem: Current optical components are reaching their physical limits. The most efficient lasers are likely to do thiscan damage lasers, prisms and mirrors. This of course affects the quality of these experiments, which sometimes require an enormous degree of precision.
Sound for lighting control
To overcome this obstacle, several leading German institutions have jointly found a very elegant solution: Instead of working on new, ever more efficient components, they have developed a technique that makes it possible to use none at all!
Instead, they exploit a completely different physical phenomenon: Sound waves. A real paradigm shift. “Modern optics are based almost exclusively on the interaction of matter with solid light,” explains Christoph Heyl, the leader of this project. “Our approach opens up a completely new field of research. »
In their published research they describe a type of invisible network made entirely of air. “We used acoustic waves to create an optical grid that locally changes the density of the air,” explains Yannick Schrödel, a doctoral student at DESY – a renowned research center that studies the structure of matter and whose particle accelerator “felt” in particular last year a Rammstein concert two kilometers away (see our article).
To achieve this, they used special speakers that can form a special pattern of more or less dense air. When the beam crosses this grid, its trajectory changes as if it had crossed different layers of the Earth’s atmosphere.
A representation of a laser being deflected by its passage through this invisible web. © Science Communication Lab for DESY
On paper, this is a very interesting approach. In theory it offers one exceptional control over the laser trajectory without distorting the signal.
Very promising initial results
And the first laboratory tests have proven very promising. The authors have already managed to redirect a powerful 20 GW laser. For reference, it’s approximate 4 trillion times more powerful than a standard laser pointer.
To achieve this, however, they had to blow up the decibel meter. “The properties of this grid are influenced by the frequency and intensity – i.e. the volume – of the sound waves,” says Schrödel. “We work at around 140 dB, which would correspond to a jet engine a few meters away,” says Heyl. “Fortunately, we are traveling in the area of ultrasound that our ears cannot perceive! »
In these tests, the researchers achieved a Efficiency of approx. 50%. A value that is still modest in absolute terms. But it’s still one very nice proof of concept. Furthermore, their simulations suggest that significantly higher efficiency can be achieved in practice.
Huge potential
And once the technology matures, this technique will pave the way for that countless very interesting concrete applications. The authors particularly cite the example of optical switches. Many systems rely on these components to on-the-fly redirect a beam while the device is in operation. By using sound instead of a combination of lenses and mirrors, We overcome the limitations of precision and speed that hinder traditional mechanical actuators. A big advantage for system performance and reliability.
Building on this initial success, the researchers will try to increase the efficiency of the system and explore further variants. So far, for example, they only worked in the air. But other gas mixtures could also pave the way to even more applications in future-oriented areas. We can quote that Quantum mechanics, particle physics or even nuclear fusion. “We will try our luck with other gases in order to exploit other wavelengths and thus also other geometries and optical properties,” concludes Heyl.
The text of the study can be found here.