NRL Tests Underwater Laser Communications

The U.S. Naval Research Laboratory (NRL) is preparing for another set of field tests that could be used to develop underwater laser communications capability.

The NRL completed its first undersea laser-generation field demonstration in May 2010 and will look to expand on those tests this June, says Ted Jones, a civilian physicist and team research leader for the NRL plasma physics division.

The test involves using a laser to ionize the water, Jones says, with high-intensity pulses lasting nanoseconds. “It gets the water superheated, acting like a piston,” he says.

The ionized water generates an acoustic supersonic shock wave that can be shaped and directed by simply varying laser settings, Jones says. That wave can be used to generate high-resolution acoustic images, or high data-rate communications.

The first demonstration last year used small-energy laser pulses. In this year’s demonstration, Jones says, the lab will try to send the wave in different directions and angles. “You have to shape the piston,” he says.

The tests grew out of research into underwater weapons explosions, which analyzed the hydrodynamics involved in those events and their blast effects. Water is a good candidate for acoustic communications. “It is so conductive,” Jones says.

The laser is needed to create the heat and shock wave. The trick now is to tune the lasers so they operate as needed. “Lasers are finicky,” Jones says. “They don’t like humidity, and many older types have poor energy efficiency, though newer types are better.”

Still, the potential is worth the effort. Not only could subsurface acoustic communications help create even better links for undersea Navy assets, but laser-generated communications in that realm also could be adapted to provide better intelligence, surveillance and reconnaissance (ISR) to locate threats such as mines. “There is a large scope of applications,” Jones says.

The development of laser-generated undersea acoustic communications and ISR also could help the Navy justify and continue its research and development of laser-based weapons.

“The Navy is developing laser weapons applications,” Jones notes, “and it is always looking for secondary applications.”