Nav: Home

New technology uses lasers to transmit audible messages to specific people

January 23, 2019

WASHINGTON -- Researchers have demonstrated that a laser can transmit an audible message to a person without any type of receiver equipment. The ability to send highly targeted audio signals over the air could be used to communicate across noisy rooms or warn individuals of a dangerous situation such as an active shooter.

In The Optical Society (OSA) journal Optics Letters, researchers from the Massachusetts Institute of Technology's Lincoln Laboratory report using two different laser-based methods to transmit various tones, music and recorded speech at a conversational volume.

"Our system can be used from some distance away to beam information directly to someone's ear," said research team leader Charles M. Wynn. "It is the first system that uses lasers that are fully safe for the eyes and skin to localize an audible signal to a particular person in any setting."

Creating sound from air

The new approaches are based on the photoacoustic effect, which occurs when a material forms sound waves after absorbing light. In this case, the researchers used water vapor in the air to absorb light and create sound.

"This can work even in relatively dry conditions because there is almost always a little water in the air, especially around people," said Wynn. "We found that we don't need a lot of water if we use a laser wavelength that is very strongly absorbed by water. This was key because the stronger absorption leads to more sound."

One of the new sound transmission methods grew from a technique called dynamic photoacoustic spectroscopy (DPAS), which the researchers previously developed for chemical detection. In the earlier work, they discovered that scanning, or sweeping, a laser beam at the speed of sound could improve chemical detection.

"The speed of sound is a very special speed at which to work," said Ryan M. Sullenberger, first author of the paper. "In this new paper, we show that sweeping a laser beam at the speed of sound at a wavelength absorbed by water can be used as an efficient way to create sound."

For the DPAS-related approach, the researchers change the length of the laser sweeps to encode different frequencies, or audible pitches, in the light. One unique aspect of this laser sweeping technique is that the signal can only be heard at a certain distance from the transmitter. This means that a message could be sent to an individual, rather than everyone who crosses the beam of light. It also opens the possibility of targeting a message to multiple individuals.

Laboratory tests

In the lab, the researchers showed that commercially available equipment could transmit sound to a person more than 2.5 meters away at 60 decibels using the laser sweeping technique. They believe that the system could be easily scaled up to longer distances. They also tested a traditional photoacoustic method that doesn't require sweeping the laser and encodes the audio message by modulating the power of the laser beam.

"There are tradeoffs between the two techniques," said Sullenberger. "The traditional photoacoustics method provides sound with higher fidelity, whereas the laser sweeping provides sound with louder audio."

Next, the researchers plan to demonstrate the methods outdoors at longer ranges. "We hope that this will eventually become a commercial technology," said Sullenberger. "There are a lot of exciting possibilities, and we want to develop the communication technology in ways that are useful."
-end-
Paper: R. M. Sullenberger, S. Kaushik, C. M. Wynn. "Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H2O," Opt. Lett., 44, 3, 622-625 (2019).

DOI: https://doi.org/10.1364/OL.44.000622.

About Optics Letters

Optics Letters offers rapid dissemination of new results in all areas of optics with short, original, peer-reviewed communications. Optics Letters covers the latest research in optical science, including optical measurements, optical components and devices, atmospheric optics, biomedical optics, Fourier optics, integrated optics, optical processing, optoelectronics, lasers, nonlinear optics, optical storage and holography, optical coherence, polarization, quantum electronics, ultrafast optical phenomena, photonic crystals and fiber optics.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org.

Media Contact: mediarelations@osa.org

The Optical Society

Related Laser Articles:

The sharpest laser in the world
With a linewidth of only 10 mHz, the laser that the researchers from the Physikalisch-Technische Bundesanstalt (PTB) have now developed together with US researchers from JILA, a joint institute of the National Institute of Standards and Technology and the University of Colorado Boulder, has established a new world record.
Biggest X-ray laser in the world generates its first laser light
European XFEL, the biggest X-ray laser in the world, has generated its first X-ray laser light.
Where does laser energy go after being fired into plasma?
An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde.
Over-the-counter laser pointers a threat to eyesight
Some laser pointers that can be bought over the counter are unsafe -- to the point that they can cause blindness.
Introducing the disposable laser
Since lasers were invented more than 50 years ago, they have transformed a diverse swath of technology -- from CD players to surgical instruments.
A laser for your eyes
A team of the Lomonosov Moscow State University scientists and the Belarusian National Technical University has created a unique laser, which is a compact light source with wavelengths harmless to the human eye.
New laser to shine light on remote sensing
A revolutionary new type of laser developed by the University of Adelaide is promising major advances in remote sensing of greenhouse gases.
Laser beams with a 'twist'
Using geometric phase inside lasers for the first time, researchers find a way to change the orbital angular momentum of laser beams.
New laser achieves wavelength long sought by laser developers
Researchers at the University of Bath, United Kingdom have created a new kind of laser capable of pulsed and continuous mid-infrared emission between 3.1 and 3.2 microns, a spectral range that has long presented a major challenge for laser developers.
New laser achieves wavelength long sought by laser developers
Researchers at the University of Bath, United Kingdom have created a new kind of laser capable of pulsed and continuous mid-infrared (IR) emission between 3.1 and 3.2 microns, a spectral range that has long presented a major challenge for laser developers.

Related Laser Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...