Lasers Turn Light Into Sound

A new laser technology has made it possible to turn light into sound.

Developed by scientists at the Naval Research Laboratory, the technology has the potential to expand and improve both Naval and commercial underwater acoustic applications, including undersea communications, navigation and acoustic imaging.

This process is made possible by the compression of laser pulses. Various colors of a laser travel at different speeds in water. These colors can be arranged so that the laser pulse compresses in time as it moves through water, which concentrates the light.

To convert light into sound, a laser pulse is compressed to ionize a small amount of water (give the water molecules a charge). The ionized water then absorbs the laser energy and heats up. The result is a small explosion of steam that generates a 220 decibel pulse of sound.

A laser pulse can travel through either air or water, but the concentration effects are much stronger in water.

A well-tuned laser can travel many hundreds of meters (yards) through air, then quickly compress once it enters the water, making it possible for aircraft to send messages underwater.

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