US Navy researchers want to use a special laser to remotely generate sound underwater. It can be used for communication with submarines, sonar imaging and confusing enemy subs.

The laser is tailored so that once entering into salt water it focuses itself, using the liquid as a sort of lens. This creates a small zone of ionization, which quickly absorbs laser energy, causing a loud explosion of steam. Dr. Ted Jones, who leads the Naval Research Laboratory team, says the bang generates sound pressure of 220 decibels, or about the same level as an active sonar generates.

At the same time, in the air the beam can travel hundreds of meters unhindered. The equipment is compact enough to be used from an aircraft. Navy scientists say it could be used to deliver messages to subs on patrol from passing planes without the need for the submarines to surface.

On the civilian side, the team suggest the laser mounted underwater can be coupled with a steering mirror to generate arrays of underwater acoustic sources, which can be helpful for sonar imaging.