MIT Researchers Can Use Lasers to Transmit an Audible Message to a Person

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Soon enough we’ll be able to send an audible message to a person with nothing more than a laser. Well, it won’t be used in day to day life, but in life-threatening situations such as warning someone about a possible shooter for example. And it also comes with a catch.

Researchers from the Massachusetts Institute of Technology’s Lincoln Laboratory have just published in The Optical Society (OSA) journal Optics Letters two laser-based methods that can transmit tones, music and recorded speech at could volume.

According to Charles M. Wynn, the research team leader, this new tech 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.” He added that you could use the system from a distance and beam that information to someone’s ear.

Fast Laser Beams, Water, and Sound to Communicate

The method is based on the photoacoustic effect, and the research team created the sound by using water vapor from the air which absorbs light, and it also works in dry conditions because there’s always water in the air:

“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 two methods grew from a technique known as dynamic photoacoustic spectroscopy (DPAS). Researchers have previously developed chemical detection for it and discovered that it can be improved by a laser beam that travels with the speed of sound.

The first author of the paper, Ryan M. Sullenberger, explains that the method works only with sweeping a laser beam at the speed of sound, which at a wavelength, “absorbed by water can be used as an efficient way to create sound.”

Changing the length of the laser sweeps, researchers could encode different frequencies in the light. This technique can be used from a certain distance and sent to a person, but the message can also be sent to more individuals.

The researchers are testing both this new laser technique and a traditional method to see how they work at a longer range, added Sullenberger:

“We hope that this will eventually become a commercial technology. There are a lot of exciting possibilities, and we want to develop the communication technology in ways that are useful.”