

Using Lasers to Find Land Mines and IEDs - jcr
http://spectrum.ieee.org/semiconductors/optoelectronics/using-lasers-to-find-land-mines-and-ieds/0

======
unwind
So, basically they're creating a lasing region of space, in mid-air, at a
distance of 30 meters (~100 feet):

 _The beam is transmitted through a lens that focuses it on a spot 30 or so
meters away; there it converges and then diverges, giving this region an
hourglass shape. Because the laser pulse is very brief—on the order of
nanoseconds—the intensity is high enough to break molecules of oxygen into
their constituent atoms over a few millimeters in the thin midsection of the
hourglass. This happens so rapidly during the pulse that the same pulse
subsequently excites many of the oxygen atoms into a high-energy state,
creating what's called a population inversion. This unstable condition then
leads to the familiar laser chain reaction in which an excited atom drops to a
lower energy state, emitting a photon of a particular wavelength, and that
photon in turn stimulates another excited atom to emit a photon of the same
wavelength and phase._

The thus excited region of space emits two laser beams, one in the direction
of the original "trigger" beams, and one _in the opposite direction_ i.e. back
at the source. The intensity is said to be around 1,000,000 times that of the
ambient radiation in that wavelength, so it's "easy" to detect. And the beam
carries information about the molecular mix in the generating volume of space,
which is of course the core feature here.

That is ... pretty close to being magic, in that "naah, that can't be
possible!" way that is so fantastically neat.

Too bad the triggering impulse (heh) to develop this is something as nasty as
land mines and IEDs, the technology itself is just beautiful.

~~~
lallysingh
Sure, but how do you get the sharks 100 feet up? And won't they suffocate
without water?

------
tocomment
That's pretty amazing! I've always wondered if you could have a device that
detects ice (using lasers, or other optical methods) and place one looking
down at the road in front of each tire.

Your car could then warn you when it starts seeing ice, and possibly even take
measures to improve control.

I know a lot of times the road will be wet and it will be below freezing but
there's no ice, but it's scary to drive because you know you could encounter
ice at any time.

------
nemo
If I were an Afghanistani/Iraqi/whoever planting IEDs/mines trying to defeat
this, I'd make small bundles with explosives in them and sprinkle them in
random areas to create large enough numbers of false positives to make using
this onerous.

Still, this is a promising sounding tech. for detecting mines in past
battlefields, ordnance, mercury and so on. Hope the idea is developed in a
workable way.

~~~
jcr
It seems you're limiting your perspective to recent conflicts. Mines and
unexploded ordinance are a huge and long-standing problem across the globe.
For example, it is still common for explosives from the first world war, a 100
years ago, to be found in Europe. Similar is true for nearly every other
conflict in history.

An interesting point the article did not mention is how some forms of
munitions tend to release more identifiable gases as they slowly decay over
time. This is one of the reasons why using trained dogs has been effective to
locate mines. If they can get this laser and radar tech working effectively,
it stands to reason this tech will be especially useful for finding and
clearing old mine fields.

Mines are a terrible problem, but tech like this has a chance of saving a lot
of innocent lives.

~~~
Wingman4l7
There's been a lot of success in using trained rats to detect landmines --
they're cheaper to care for / transport, quicker to train (IIRC), and too
light to set off the mines.

I've also read of more unusual / interesting detection techniques researched,
like bees, and my personal favorite, the seeding by air of bioluminescent
bacteria that feed off of said gases.

~~~
kroy
In case anyone is interested in reading more about mine-detecting rats, you
can check out an organization called Apopo. They're pretty cool, and you can
even adopt your own rat!

<http://www.apopo.org/en/>

------
gwright
All they need to do is scale this up a bit, put it in orbit and they've got
Star Trek sensor arrays.

