Acoustic Waves Guide Light: Air-Induced Deflection of Laser Beams

A laser beam navigates through a lattice of air produced by a loudspeaker-reflector configuration. This beam undergoes interaction with the lattice and gets deflected without making physical contact. Courtesy: Science Communication Lab on behalf of DESY.

Pioneering Approach Redirects Laser Beam Through Sonic Waves

A groundbreaking technique allows laser beams to be redirected solely by utilizing air. A transparent lattice consisting entirely of air not only remains impervious to laser beam damage but also maintains the beam’s original quality, according to an interdisciplinary team of researchers published in the journal Nature Photonics. A patent application for this technique is currently in progress.

Methodology and Fundamental Concepts

This avant-garde method employs sonic waves to modulate the air through which the laser beam travels. “An optical lattice has been created using acoustic density waves,” elaborates lead author Yannick Schrödel, a doctoral candidate at DESY and Helmholtz Institute Jena.

By employing specialized loudspeakers, the scientists construct a pattern of varying air densities, thus creating a striped lattice. Analogous to the way variable air densities bend light in Earth’s atmosphere, this density pattern functions as an optical lattice that alters the laser beam’s trajectory.

“Diffracting light via this lattice enables more precise control over the laser beam compared to atmospheric deflection,” adds Schrödel. “The characteristics of the optical lattice are determined by the amplitude and frequency—or in layman’s terms, the volume—of the sonic waves.”

Experimental Outcomes and Future Prospects

Preliminary lab tests showed that a potent infrared laser pulse could be rerouted with a 50 percent efficiency using this method. Computational models suggest that even greater efficiencies could be achieved in the future. To conduct the initial test, the researchers had to amplify their specialized loudspeakers to maximum levels.

“We operate at a noise level comparable to a jet engine situated a few meters away,” says project leader Christoph Heyl from DESY and the Helmholtz Institute Jena. “Fortunately, the sound is in the ultrasound range, which is inaudible to the human ear.”

The research team envisages substantial applications of this technique in high-performance optics. In their tests, they used an infrared laser pulse with a peak power of 20 gigawatts—equivalent to the energy output of roughly two billion LED light bulbs. Such high-power lasers are commonly used in material processing, fusion research, and advanced particle accelerators.

“Traditional optical elements like mirrors, lenses, and prisms are constrained by material properties and are susceptible to damage from high-powered lasers,” Heyl explains. “In contrast, our method enables non-contact, quality-preserving deflection of laser beams.”

Extended Applications and Future Explorations

The concept of sonic manipulation of laser light is not restricted to the formation of optical lattices; it could potentially extend to other optical devices like lenses and waveguides.

“We’ve been contemplating this approach for some time and initially deemed the necessary sound levels as technically impractical,” says Heyl. “Nevertheless, with assistance from researchers at the Technical University of Darmstadt and the company Inoson, we persisted and eventually succeeded, initially using regular air. We intend to experiment with different gases to explore various optical properties and configurations.”

The capacity to deflect light directly into ambient air has already been proven and shows significant promise, particularly as a rapid switch for high-power lasers. “The full extent of touch-free manipulation of light and its broader applications remain speculative at this point,” concludes Heyl. “Traditional optics primarily focus on light-matter interactions. Our methodology heralds an entirely new paradigm.”

Reference: “Acousto-optic modulation of gigawatt-scale laser pulses in ambient air” by Yannick Schrödel et al., 2 October 2023, Nature Photonics. DOI: 10.1038/s41566-023-01304-y

Collaborators in this research include the Technical University of Darmstadt, Aalen University of Applied Sciences, Universität Hamburg, Inoson GmbH in St. Ingbert, the Helmholtz Institute Jena, and DESY.

Frequently Asked Questions (FAQs) about Acousto-optic modulation

More about Acousto-optic modulation

• Nature Photonics Journal Article
• DESY Research Institute
• Helmholtz Institute Jena
• Technical University of Darmstadt
• Aalen University of Applied Sciences
• Universität Hamburg
• Inoson GmbH in St. Ingbert
• Principles of Acousto-Optic Modulation
• High-Performance Optics
• Patent Application Process for Optical Technologies