Planes To Shoot Lasers To "Talk" To Submarines?

Lasers that can create loud bangs under the sea might someday replace sonar for sending messages to submarines (pictured), Navy physicists announced in May 2009. The self-focusing beams heat tiny amounts of water in the sea to create "little pistons of steam" that expand at supersonic speeds. Photograph courtesy Commander Submarine Group 9, U.S. Navy

From The National Geographic:

Lasers that can create loud bangs under the sea might someday replace sonar for sending messages to submarines, Navy physicists have announced.

Conventional sonar mapping uses pulses of sound, which require towed arrays of speakers and receivers.

"You have to pull [the array] with a vessel," said Ted Jones, a plasma physicist with the U.S. Naval Research Laboratory in Washington, D.C.

"It's slow and expensive. It might take hours or even days to search a large area."

The new technique—a 21st-century form of Morse code—uses self-focusing laser beams to superheat BB-size quantities of water up to 70 feet (20 meters) beneath the waves.

The result is "a little piston of steam" that expands at supersonic speeds, creating an underwater bang loud enough to be heard miles away, Jones said.

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