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Navy Scientists Develop Laser For Underwater Communication

Posted by ScuttleMonkey on from the can-you-see-me-now? dept.

Researchers at the Naval Research Laboratory claim to have come up with a better tool for underwater acoustics. The new system uses laser light to create sound underwater from a distance. This technology could allow planes a much easier method of communicating with submarines without the need for a floating buoy. "Efficient conversion of light into sound can be achieved by concentrating the light sufficiently to ionize a small amount of water, which then absorbs laser energy and superheats. The result is a small explosion of steam, which can generate a 220 decibel pulse of sound. Optical properties of water can be manipulated with very intense laser light to act like a focusing lens, allowing nonlinear self-focusing (NSF) to take place. In addition, the slightly different colors of the laser, which travel at different speeds in water due to group velocity dispersion (GVD), can be arranged so that the pulse also compresses in time as it travels through water, further concentrating the light. By using a combination of GVD and NSF, controlled underwater compression of optical pulses can be attained."

22 of 83 comments (clear)

  1. underwater lasers? by myVarNamesAreTooLon · · Score: 5, Funny

    ...but do they have plans to attach them to sharks?

    1. Re:underwater lasers? by Bovius · · Score: 2, Insightful

      I think editor was just digging for shark comments on this one.

  2. How does this NOT pose a danger... by mysidia · · Score: 2, Interesting

    To Swimmers and wildlife, when a plane is shooting this giant high-powered laser into the water, to communicate with the submarine?

    achieved by concentrating the light sufficiently to ionize a small amount of water, which then absorbs laser energy and superheats. The result is a small explosion of steam, which can generate a 220 decibel pulse of sound.

    1. Re:How does this NOT pose a danger... by John+Hasler · · Score: 2, Informative

      Swimmers would be in about the same danger of being zapped by this thing as they would of being hit on the head by one of the air-dropped buoys that it would replace.

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    2. Re:How does this NOT pose a danger... by Mozk · · Score: 2, Informative

      Interesting note: it also occurs the other way around with sonoluminescence. Intense sound through a liquid can create light.

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  3. Whale/sonar people are going to love this one by BigSlowTarget · · Score: 5, Insightful

    I don't know how the audio volume of this system compares with sonar systems (though the article's 220db and 160db from http://www.oceanmammalinst.org/mgpaper.html kind of gives clues and weakly suggest might be as much as 64x), but I suspect the people who oppose the use of sonar by the navy on the theory that it hurts whales are going to go nuts over this one.

    There is no where near enough info to actually assess any kind of threat, but I'm sure the panic button will be hit anyway.

    1. Re:Whale/sonar people are going to love this one by fluffy99 · · Score: 3, Informative

      Active Sonar output is limited by cavitation. That is the boiling of the water on the surface of the transducer, which acts like a blanket attenuating and distorting the output. In general that means under 200 dB. Still plenty to cause problems with local wildlife. Active sonar is not used very often at its also like turning on a spotlight in a dark room.

    2. Re:Whale/sonar people are going to love this one by John+Hasler · · Score: 2, Interesting

      The 220 db figure is probably the sound pressure right at the surface of the bubble. That tells you nothing useful as to the hazard to wildlife: depending on the pulse energy and repetition rate the bubbles could be as small as a few microns in diameter and the sound level nearby quite modest. The ability to create large "virtual" phased arrays should also reduce the need for the very high energy pulses used in some current systems.

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    3. Re:Whale/sonar people are going to love this one by anotherhappycamper · · Score: 3, Insightful

      I hope it does push the panic button. It is one thing for us to defend ourselves. It is quite another for us to make another species miserable or extinct while attempting to optimize a way to defend ourselves from our own fears. Public outcry and discussion can give us pause so that we can investigate whether the effectiveness outweighs the possible ethical costs, and hopefully come up with a thoughtful solution.

    4. Re:Whale/sonar people are going to love this one by maeka · · Score: 2, Interesting

      Really?

      Let's play devil's advocate and assume the Navy is needed and capable of "defending ourselves."
      How many whales are worth one human life? How much whale misery is equal to human misery? What are the ethics of letting humans (of any nation) die in order to save a whale or give said whale a better life?

      I ask this simply because you put it in the context of defense, not (financial) cost.

      This is the one environmental question I don't see asked enough. Choosing the less effective method for environmental reasons - be it the less effective military communication method or the more costly energy production method - can directly harm (or put in harms way) people in order to protect animals.

    5. Re:Whale/sonar people are going to love this one by drerwk · · Score: 3, Interesting

      Get back to me when there are 6 billion whales with and expected increase of 3 billion over the next decade or so. I would be willing to give up a nation of people if I could put the ocean back the way it was a hundred years ago.

    6. Re:Whale/sonar people are going to love this one by woolpert · · Score: 2, Insightful

      Who, exactly, are you willing to kill / let die to achieve your goals.

    7. Re:Whale/sonar people are going to love this one by drerwk · · Score: 2, Interesting

      Intro to moral philosophy was not my best class. But a lottery would certainly be fair. Instead I would suggest we outlaw those activities that cause harm, let's not argue about the method of measurement, to the ocean, or specifically whales. And if in fact as some ancestor post suggested this will result in human death, then so be it. You know, it is demonstrable that lowering the speed limit on highways reduces death by collision, but we re perfectly happy to leave the limit high for our convenience. Seems like a similar argument to me.

  4. Re:Operational security? by Kamokazi · · Score: 2, Interesting

    They would probably have regulations on when this method of communication can be used once (if) it is put into use.

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  5. Re:Operational security? by Vahokif · · Score: 3, Interesting

    Encryption?

  6. And the things living around it? by Anonymous Coward · · Score: 3, Informative

    I wonder how many marine animals we'll cause to go deaf from this, which would probably end any chance of survival for those affected. http://www.makeitlouder.com/Decibel%20Level%20Chart.txt 220 decibels is incredibly loud in the air, I can only guess the extended intensity it travel with underwater...

  7. Re:Operational security? by cwebster · · Score: 5, Informative

    The issue isnt eavesdropping, its that the mere act of communicating gives your position away to everyone when wants to know.

  8. bad acronym by Jeek+Elemental · · Score: 3, Funny

    they should call it NSFW (Not Safe For Whales)

  9. Re:Operational security? by canadian_right · · Score: 2, Insightful

    Nothing.

    Obviously you don't communicate directly with subs during hostilities using methods that can be easily overheard.

    Why do so many slashdotters think that experts have not thought of their brilliant insight many years ago?

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  10. They Should Call It... by FireIron · · Score: 2, Funny

    Subsurface Hydro-Acoustic Radiation Communication System (SHARCS)

  11. Correction by inKubus · · Score: 2, Funny

    They should call it Subsurface Hydro-Acoustic Radiation Communication System with Lasers (SHARCS with Lasers)

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  12. Re:Operational security? by ceoyoyo · · Score: 2, Informative

    Dropping a sonobuoy and transmitting a message tends to have the same effect.

    There are apparently circumstances when you need to have a chat with a submarine and it's worth giving away that there's a sub somewhere within X km, in some direction. On the other hand, since you don't have to drop a buoy every time, with the laser system you could potentially go around broadcasting some dummy messages too.