High Def Video Underwater

Maybe something like this....?

http://spie.org/newsroom/6070-novel-laser-diode-technology-for-free-space-communications

Not exactly.But a very informative link nonetheless.Thanks!

As I remember it, in the article I read,the laser was used to generate a high frequency sound signal that was impossible with the state of the art piezo-mechanical transducers at that time.

The laser created a cavitation bubble that collapsed,which in turn generated a shock wave in the water.

A single bubble was impossible to generate,so groups of bubbles were sent as a single bit.

This method also made decoding difficult for anyone trying to decode a single bit.It would look like noise to the uninformed.

The bubble collapse emitted a particular frequency dependent on bubble size,external pressure on the liquid transducer, the type of liquid/mixture,the coupling membrane material composition and thickness,and other factors not enumerated in the article.

I do not recall the frequency,but apparently a particular wavelength had been found that was transparent in seawater at that particular frequency.

It was being tested and evaluated for military purposes.

Odd that I can recall so much about it,but cannot recall where I read it,but I know it was approximately 10 years ago.

Sort of like recalling events from your childhood more clearly than what you ate for breakfast yesterday morning.

Technology has probably moved far beyond this stage by now,and the prototypes are probably boat anchors by now.

Thanks to all for the feedback.

How about Lasers generate underwater sound?

LIB or laser induced breakdown is becoming a wider field, now has many spectroscopic applications for PMI (positive materials identification).

Note that since the pulse is temporally compressed in the water, and somewhat self-focusing, this will lead to a cavitation, laser induced breakdown. It will produce a very sharp acoustic ping with high intensity.

Obviously, sonic imaging relies on very short pulses, to that resolution of return pings has the capability of being resolved to smaller dimensions.

At first, I read the title as High Def Video Underwear.

Or did you mean synthetic aperture SONAR?

http://www.krakensonar.com/en/

I think laser diodes are more for high speed communication underwater.

Maybe this?

https://www.sciencedaily.com/releases/2009/09/090904165241.htm?trendmd-shared=0

A problem with underwater communication is that bandwidth and range are incompatible: High data rate means short range.

http://helper.ipam.ucla.edu/publications/quant2012/quant2012_10816.pdf

Does the optical part of that graph include all wavelengths extending into the NIR?

I suspect it's the blue-green band. Water absorbs most electromagnetic radiation except for a narrow window in the blue-green optical region.

https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water