"Matt Barrow" wrote in message
...

According to a radio show last night, the lasers have been all "green"
except one. Sounds like it might be the laser pens, but do those have
enough
strength to light up a target several thousand feet away?

I have a bunch of high power visible lasers. All except one are Argon or
Argon / Krypton Gas Ion lasers. Argon produces a mixture of blue and green
colours and Krypton generally produces red. They range in output from 3 to
13 watts. The largest is a mixed gas Argon / Krypton. The same laser with
an Argon tube can produce over 20 watts. But they're *big*. The power
supply is the size of a small refrigerator. The head is over 7 feet long
and weighs about 200 lbs. They require 480V AC service and draw about 50
amps. They also require water cooling at a rate of about 3 US gallons per
minute. Hardly portable. And, they cost at least 25K for a decent used
one. A high level of technical expertise is required to operate them. Go
here and look for "Ion Lasers".

http://www.cohr.com/

There are portable systems that can produce power in these ranges though.
More later. I used to have one near the top of the CN Tower in Toronto. It
was a large frame Argon laser and produced about 20 watts. It was focused
on the ground about 3 miles away. I can't remember what the power level was
at the ground. But it was well below 2.5 mw/cm (the safety limit for brief
exposure). However, even at that level it's still bright enough to
temporarily affect night vision after a brief exposure.

The reports indicate a green beam. There are a few types of solid state
lasers that produce green at high power. Here's one of the largest:

http://www.laserfantasy.com/products_i2000.asp

Again, it requires a fair bit of power and water but I've seen portable
versions of them. They're expensive (~50K US) and require technical
expertise to operate. So I don't think they're practical for covert
terrorist activities.

On the small scale, there is a device (I happen to have one) that could be
used as a turbocharged pointer. Go to
http://lasers.mellesgriot.com/default.asp and look at "Diode Pumped Solid
State Lasers". These produce about three watts of green and only draw about
150 watts. They could easily be powered by a small Inverter in an
automobile. Cost is about 12K US new.

Now for a reality check. To actually blind someone at a distance of several
miles is practically impossible. It would require a very high power laser
and sophisticated tracking equipment. Even then, one would have to
intentionally stare at the offending beam for permanent damage to occur.
The same tracking system with a smaller (~2 watt) laser could be used to
make it impossible to carry out the visual portion of an approach. But, and
anyone experience with laser shows will tell you, holding a beam steady at a
distance of miles is really tricky stuff. However, I think that an amateur,
armed with a 3 watt DPSS laser could cause some serious problems just by
sitting in a vehicle at the end of a runway and eyeballing shots at incoming
planes.

Now, in anticipation of the question, here's what it feels like to get
zapped by one of these things at a distance. (It's happened to me many
times.) You will be momentarily blinded. It won't incapacitate your vision
for more than a few seconds, assuming that you blink. You will want to
abort the approach, not because you won't be able to land, but because the
same thing might happen again. Obviously you'll want to alert the police
and FSS or Tower. If the idiot shining the beam leaves it on, you should be
able to see their location. The colour produced by these devices is an odd
sort of green that doesn't occur in nature an is unmistakeable.

Here's some links on laser safety.

http://www.laserist.org/Laserist/Safety.html
http://www.laserfx.com/Science/Science4.html

moo