Originally posted by NothingMakesSense
I have a question about lasers:
Since lasers are just concentrated light, could they be foiled by a mirror?
If so, the obvious defense is to coat all our armoured vehicles with a reflective substance.
Originally posted by Amur_Tiger
...if you use the same reflective material that the laser uses to get the ray concentrated then it would work. Also a good cooling system would make
this a non-issue, Liquid Ox tanks on the outside could actually become a good thing.
Lasers and mirrors...
ATS member NothingMakesSense
, while it is true that lasers are "just concentrated light" (amplified), mirrored surfaces may not be as
advantageous as one may think.
ATS member Amur_Tiger
rightly refers to specific materials used to reflect laser energy, however considering liquid oxygen as a coolant to keep
a concentrated heat source such as a megawatt laser from destroying a target will make for some rather spectacular fireworks.
Here are a few points of clarification on laser reflectivity...
(I actually posted this information in another related thread but I did a slight rewrite to cover this subject matter)
1.) No surface is 100% reflective.
The energy that is not reflected is dissipated by the surface as heat. As heat builds up, the reflectivity of the surface will decrease, and it
decreases exponentially from that first contact. This will impede the time it takes a laser to inflict damage on a target, but at the mega-power
levels of battlefield lasers it would be measured in nano or milliseconds as opposed to seconds.
It is helpful to realize that even mirrors for lower powered industrial lasers need to be water cooled, in spite of being over 99.5%
reflective for this reason.
2.) For a surface to remain highly reflective, it has to be kept incredibly clean.
A $600 germanium mirror for a 500 watt CO2 laser can be
easily destroyed in a fraction of a second if it has so much as the residue of a finger print that has been wiped off with a lens cloth without
benefit of cleansing solvent.
For tanks/aircraft/missiles to be able to reflect enough of a weapons-class laser beam
to be impervious, they'd need to be polished to an
optical grade and wiped off to clean-room specs. Not the sort of thing that's practical in combat.
3.) Surfaces are only reflective to a certain range of wavelengths;
in other words, what mirrors light in our visual wavelength does not
necessarily mirror light in another wavelength.
As an example, the $600 germanium mirror I talked about above is reflective to CO2 lasers in the far infrared wavelengths (10.6 microns), it is glossy
black and completely unreflective to visible light
which as a reference centers around .4 microns.
On the other hand, a mirror for a Ruby laser, which outputs radiation at .69 microns is standard silver. If you switch the two mirrors with their
respective lasers, each will shatter immediately.
If an enemy were to armor their vehicles/missiles with a reflective coating, provided they could keep it clean and polished in battlefield conditions
(impossible unless in a particle free perfect vacuum), the resonant cavity optics of the laser could theoretically be changed to amplify a wavelength
that the reflective surface would be vulnerable to.
[Edited on 18-5-2004 by intelgurl]