Well according to this paper, laser for detection & laser
for communication actually are in the same principle.
http://www.darpa.mil/sto/maritime/slc.html
Blue Laser for Submarine Laser Communications (SLC) and
Non-Acoustic Anti-Submarine Warfare (ASW)
Program Manager: Dr. Larry Stotts
The goal of the DARPA Blue Laser for Submarine Laser Communications
(SLC) and Non-Acoustic Anti-Submarine Warfare (ASW) program is to
develop a high wall-plug efficient, Blue Light (455nm), Solid-state
Laser.
Foreign submarines are quieter than ever before, and there is a
pressing need for improved ASW capabilities, particularly in
shallow water (above the thermocline) and littoral areas of
operations. Coordination between multiple assets such as aircraft,
surface ships, and submarines is critical to an effective ASW
campaign. Integration of submarines into an overall ASW effort,
arguably the most effective platform for wide area search and
tracking, has traditionally been hampered by lack of or minimal
communications to the submarine while deep.
The Navy is currently investing in new and previously demonstrated
techniques for communicating with submarines at speed and depth for
coordinated ASW operations. These techniques most commonly use
either trailing wires or towed buoys for submarine communications,
which impose limitations on the submarine's maneuverability and
stealth, and therefore negatively impact the submarine's ability to
fully conduct ASW operations. An airborne laser which could
penetrate shallow water would permit submarine communications
without the restrictions of floating wires or buoys.
This program is intended to develop the world's first wall-plug
efficient laser that operates both at an optimum water transmission
band of open ocean water and at the wavelength of a Cesium Atomic
Line Filter. This laser has the potential to improve the
detection depth of a NAASW lidar system by a significant factor for
the same reasons it could improve submarine
communications.
