US Navy boffins say they have developed a method which could allow aircraft to communicate with submarines using frickin' laser beams.
Dr Ted Jones of the Naval Research Laboratory has developed methods of generating acoustic effects in water by firing laser pulses into it. According to the lab:
Optical properties of water can be manipulated with very intense laser light to act like a focusing lens... In addition, the slightly different colors of the laser can be arranged so that the pulse also compresses in time as it travels through water, further concentrating the light. Controlled underwater compression of optical pulses can be attained.
Apparently the NRL's cunning self-generated water lens and colour time-compression tech allows a laser beam to generate a tailored underwater "explosion of steam" which can emit a sonic pulse at 220 decibels - all without any hardware actually in the water at all. Jones and his fellow maritime boffins think that the laser beam could travel "many hundreds of meters through air" before generating its acoustic effects in the water.
This would allow a aircraft high above the sea to fire a laser downwards, generating sound pulses which could be received by underwater telephone gear aboard a submerged submarine. At present, communication with subs at depth generally requires the use of a floating buoy*.
Another possible application would be the generation of sonar pulses without the need to put active equipment into the water. Receivers would still need to be put into the sea to pick up the echoes - either lowered from a hovering helicopter or in dropped buoys - but such kit would be less complex and expensive than present-day gear which contains an emitter as well. It would also be harder for hostile sub commanders to locate their enemies.
According to the NRL, the new laser acoustics could also enhance the effectiveness of underwater active sonar. ®
*There is the option of very low-frequency radio sent from a large shore station, but this requires the sub to come fairly shallow and stream an antenna.