I been thinking of the laser flare system described in Practical
Sailor. They talked about the green one being much more (100x)
visible than the red one(due to relative sensitivity of the human
eye). Of course, this is not surprising, ppl have used dim red lights
for years for indicators when they didn't want to spoil their night
vision. So, it would seem to make a lot of sense to spend about 2x
the money to get 100X the apparent brightness.
These laser flares are limited (by the FCC I think) to less than 5 mW
of power and are very directional. Existing rescue strobes all seem
to be white which seems to be a waste of power. Why not make them
emit green light? I know green flashlamps exist.
Furthermore, why not make a laser-like device to emit monochromatic
green light in all directions. However, instead of having it be
coherent like a laser, it would only be monochromatic. This could be
done by leaving off the cavity end mirrors of the laser so the light
is emitted in all directions. Not being a laser, the power limitation
would not apply and it could put out a lot more power. Furthermore,
instead of having it be continuous, make it pulsed both to attract
attention and conserve power. It could even be limited to emit into
an annular cone corresponding to the area from the horizon up to some
angle determined by optical cavity geometry and probability of
detection from far away.
Search and rescue ppl could use an automatic search device with a
filtered optical amp. This detector would be filtered to allow only
the monochromatic light to pass in order to greatly improve the signal
to noise ratio. It would also use a "Lock-In Amplifier" synchronized
with the emitting strobe to only amplify the signal and reject the
background noise. Of course, you ask how it would be synchronized
with the emitter. Well, we have all seen those watches that are
synched with the NBS atomic clock via a radio receiver inside the
watch, well the strobe would be linked in the same way as would be the
rescue detector. This way, the strobe could be detected at far
greater distance than just detection by eye or even conventional night
vision devices. It would even be visible in daylight to this rescue
detector since the detector is filtered and "locked-in"