Why might the U. S. Navy be interested in a blue-green laser for satellite to submarine optical communications
969433
The blue-green is so it will penetrate the oceans.  (Water absorbs red and other colours).\n\nCommunications by lasers cannot be listened to by enemies or other parties unless they are directly in the beam's path.  Combined with encryption the laser communications are very secure.\n\nAlso the current VLF (Very Low Frequency) communication systems cannot transfer data very fast so even small messages can take many minutes to transmit.  Lasers are capable of very high data rates (just look at CDs and DVDs).
1120999
No, be nice, but Reagan couldn't make it work. We're testing a system aboard a mod 747, and ground based systems, but nothing powerful enough yet to penetrate the atmosphere. Other anti-missile missile systems being tested for regional defense. Japan is partnered with us on that among others.
1109557
1) You must first of all be aware that radio waves, light, infrared, x-rays, all these are electromagnetic radiation, only with different frequencies; they are pure energy, without mass, transmitted through space by photons at the speed of light. That is the fastest way of communication there can be in the universe, assuming that nothing travels faster than the speed of light.\n\n\n2) Radio waves were chosen from the electromagnetic spectrum because they include the Water Hole, which is the band of electromagnetic frequencies between 1420 MHz and 1640 MHz. This is the band between the hydrogen line and the strongest hydroxyl spectral line, and is notable because it is a quiet region between two notable frequencies; The combination of hydrogen and hydroxyl yields water (the "water" part of the name); the "hole" part refers to the sudden drop in radio noise (the universe background radiation) within this band. Several SETI programs, including SETI@home search in the Water Hole.\n\n\n3) It has been proposed that higher frequency signals, such as lasers operating at visible light frequencies, may prove to be a fruitful method of interstellar communication; at a given frequency it takes surprisingly small energy output for a laser emitter to outshine its local star from the perspective of its target.\n\nOther more exotic methods of communication have been proposed, such as modulated neutrino or gravitational wave emissions. These would have the advantage of being essentially immune to interference by intervening matter, but are very difficult to generate or detect with current technology.\n\nSending physical mail packets between stars may prove to be optimal for many applications. While mail packets would likely be limited to speeds far below that of electromagnetic or other light-speed signals (resulting in very high latency), the amount of information that could be encoded in only a few tons of physical matter could more than make up for it in terms of average bandwidth.Starting in 1979, Robert Freitas advanced arguments for the proposition that physical space-probes provide a superior mode of interstellar communication to radio signals, then undertook telescopic searches for such probes in 1979 and 1982.
985973
Actually this is quite possible.  The key is that the laser emits a wavelength which interacts with the N2, O2, and CO2 in the air.  Each of those molecules have specific absorption and emission spectra.  As they absorb the frequencies (research their respective absorption spectra through Wikipedia or Google) of the radiation (not necessarily light) that passes through them, the light will scatter with re-emission at different frequencies (their respective emission spectra), as if reflecting off of  an object.  They wavelengths are the important part, and not necessarily the coherency (as inherent in lasers) which tends to constructively interfere to produce "laser speckle."  The primary reason one might choose a laser is ability to key the energy on the specific frequencies of interest and to control the path of the light.  You would want mirrors on the ceiling and the floor to be perfectly aligned to allow the reflected beams to cover more area of the "laser wall" with multiple reflections from partial reflectors distributing the energy from a primary source through multiple small holes in the mirrors on the floor.  Alignment of the optics, and stability (environmental isolation) would be critical issues of the system.  Normal vibrations and movements of the geology and the house will interfere with the alignment unless properly isolated from it.
685495
When i was tech support team in my high school, we had a fiber optic line coming in to main school server.  And in district office, they had OC12 and it was blazing fast!  That was 10yrs ago, so i imagine it's a light speed by now.
463556
20-1000mW is a huge range for power and cost will vary considerably.  You should also consider your other specifications (cw/pulsed, wavelength, beam stability, beam divergence) as these will vary from laser to laser.\n\nEdmund Optics (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1341)\n20 mW green for $3.2k\n50 mW green for $5.0k\n\nThinkLasers (http://www.thinklasers.com/)\n30mw-300mW green for $595-$2250\n150mW-250mW blue for $3470-$7650
9458
Try this: http://www.rp-photonics.com/pockels_cells.html
138258
try these sites: http://www.phy.ornl.gov/astrophysics/data/cf88/\n\nhttp://www.llnl.gov/science_on_lasers/07AstSpace/AS-F_Ther.html\n\nhttp://arxiv.org/abs/astro-ph/9801028\n\nI hope this helps....\n\nDon
64215
almost certainly it would be in the visible region of the spectrum. after all it does have that pretty color!\nvisible region is roughly between 400-700 nanometers wavelength.
996396
Yes, but it would be expensive to build the equipment and incredibly dangerous - imagine if the laser was hit by a small bit of space debris and the laser light moved - it would be like dropping a fire-bomb.  \n\nFar better to harvest the natural sunlight when it reaches the earth!
1026739
The dish is there in order to direct waves containing the information from the satellites into the antenna in order to give it a bigger target to hit from space. A smaller copper one would be a smaller target and more expensive
555650
I suppose it would be possible in theory. You would need an insanely bright source to project anything easily visible from Earth though. Why would you even want to do that?
207095
It was once said by Sir Townes, who is credited with inventing the first working ruby Laser, that the laser is a remarkable device looking for an application.  That was in 1968.  Today, there are numerous applications for lasers.\n\nLasers are used in medicine: for eye surgery, eye treatments and corrections to the cornea, in major surgeries ultrafst lasers are used because theyt have very short pulses with high peak power, which means they will cut the spots they are focused on while not affecting the areas around the focused spot (i.e., very little or no heat damage to surrounding tissue).  THe same principle is why we use lasers in eye surgery.  Also, different tissue absorbs different wavelengths of light, so specific wavelengths of lasers may be developed to be absorbed by specific types of tissue, like cancerous tissue, for example.  Cancerous breast tissue absorbs longer wavelengths of light than normal breast tissue, so if one spots a long wavelength (inra-red) laser beam on the breast, it only affects the cancerous issue, as it passes right through the normal tissue and doesn't affect it.  When tissue is heated, enough, it will die.  Hence cancer therapy with lasers.\n\nLasers are used in industry for materials processing (welding, cutting, drilling).  The advantage of using lasers in this area are that the cuts are very clean (or holes, or welds) and the laser can be attached to robotics that are automated to perform repetitive cuts very quickly.  Laser pulses from pulse to pulse are quite stable, when properly designed, so the repeatability in manufacturing applications is tremendous, far better than mechanical cutting, drilling, and traditional MIG or TIG welding.\n\nLaers are used for imaging.  The wavelength of lasers ranges from the deep UV (~200 nm) to the far infra-red (~10 um).  The shorter wavelengths of light act of small cameras when refelcted back from a sample, for example of human biological tissue or even molecules themselves.  So the laser can be a very high resolution imaging "camera".\n\nLasers are used in rapid prototyping for developing 3D models of products very quickly, they are used in disk drive manufacture to create "landing pads" on the disk drives for the disks to remain stable when being written to or read from, and are used in the interest of national security (i.e., weapons systems).  Lasers can be used as sensors, even very long range remote sensors (LIDAR), as motion detection devices, and as pure research tools.\n\nThere are more, but that gives you an idea.
264618
Hi, I think you're great, but i'm not going to type for 5 hours when all you needed to do was put "fibre optics" into the search engine. \nTry here:\nhttp://electronics.howstuffworks.com/fiber-optic1.htm
369059
Matter a fact I am pretty sure the U.S.Navy has an installation there anyway. Mass could fight back! There are several submarines at port there.
386893
because blue is the abundant light  wave length
505155
I think everyone else has answered this pretty clearly.  NASA looked into constructing 'solar sail ships' for space travel.  A solar powered laser placed near the sun would generate a focussed beam of mono-phasic laser light that would be directed onto an extremely light ship which maximised surface area to mass/volume by use of a special sail.  This would provide a small forward acceleration away from the laser.\n\nHowever, on Earth.. as indicated.. its a bit impracticle with present power source technologies.  You may want to think about approaching to problem of fusion power and then minimizing the technology for youur application ( a long time field of research.. not an overnight job!!).\n\nGood luck!