Looks pretty cool, i bet the water solves a lot of cooling problems down there
One thing i wonder about though: Is blue the ideal color? If you wanted to point things out in deep water would red not be a more suitable color? Obviously the water above you filters out red and green light when deeper, so it would stand out a lot more from the rest of what you are seeing. Range would be lower for red, but how far do you practcially point out things when diving? And it's not even required to hit them with the laser beam at all since you could see the direction it's pointing.
Not exactly. In 1963 a low-loss “optical window” of undersea communication for blue-green lasers between 420–532 nm was discovered. Since then research has not stopped. Blue/green laser light has the best transmissivity through water, however, some systems employ 635nm for underwater use in limited well defined applications with a few types of sensors.
The reasons that there aren't many applications of lasers in an
underwater environment is associated with the way light is transmitted
underwater.
There are two distinct causes for the energy loss of a light signal in seawater:
one is absorption and the other is scattering - 2 separate problems:
A. Most light is absorbed by water -- Water absorbs ultraviolet,
yellow and red and infrared radiation very strongly, so that beams in
these spectral regions cannot be transmitted very far -- meaning that
systems using such lasers are pretty useless. On the other hand, water
(seawater, that is) transmits blue-green light pretty well -- losing
"only" about 5% of its original intensity for every meter it transmits
through water.
B. There are often little specks of dust, tiny animals
(phytoplankton), and tiny plants (photoplankton) in water, and these
reflectd a little bit of the light, too, reducing intensity as it passes
through water. This adds to the problems noted above in Item A.
The effect of these two effects is that lasers used underwater have to be
much more powerful than those used in air, where absorption is generally
much lower than in water.
The above having been said, lasers have been used for underwater applications for quite some time.
One successful use of lasers is a laser system that provides underwater sensing -- a kind of laser radar:
Blue-green lasers located in airplanes are sometimes aimed
so that they go straight down into water that the planes are flying over.
Using very sensitive detectors in the airplane, the system detects the
small amount of light reflected both from the surface of the water and the
bottom of the harbor. This allows measurement of the water depth to
accuracies of a foot or so. The big advantage of such systems is that
they can collect data very quickly, because the airplane moves very
quickly and the lasers can be pulsed at a high rate. One example of this
is the use by Australian government planes of such a system to map their
very large coastal areas -- it's much quicker and cheaper to use a laser
radar to do this than it is to use conventional acoustic (sound wave)
sonars to make such measurements from ships.
Another laser system which is used underwater uses blue-
green lasers to communicate from airplanes to submarines. As early as
1983, experiments were done which demonstrated that this could be done
sucessfully. Investigated successfully also were satellite to submarine communications
using blue-green lasers which not much has been published about for obvious reasons.
Beyond this, there haven't really been too much uses of lasers
underwater. Bob Ballard -- the man who mounted the expeditions that found
the Titanic in the North Atlantic Ocean -- expressed some interest in
trying to use blue-green lasers to assist in taking pictures of the
Titanic, but found out that development of an appropriate system would be
very expensive and not too much better than just using high power
spotlights... which he ultimately used instead of lasers.
For more information see
Electromagnetic Absorption by Water here:
https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water
A more detailed information with great graphics, see:
Water absorption spectrum
Technical article:
Absorption and attenuation of visible and near-infrared light in water: dependence on
temperature and salinity here:
ftp://misclab.umeoce.maine.edu/users/optics/classFTP2015/Labs/Lab2_resources/Pegauetal1997.pdf
Interesting paper from 1983 on military applications of blue-green lasers:
http://www.google.com/url?url=http://www.publications.drdo.gov.in/ojs/index.php/dsj/article/download/6173/3278&rct=j&frm=1&q=&esrc=s&sa=U&ved=0ahUKEwjYu7OiydHPAhVDPD4KHVCEBVs4ChAWCBowAQ&usg=AFQjCNGGhfUkWXE-TJQjZqO7Y5W_Mr63EQ
Good site on Ocean Optics see:
http://www.oceanopticsbook.info/view/overview_of_optical_oceanography/inherent_optical_properties
