Do we have any laser experts here? I am wondering if there is any way to 'defeat' a laser.

Lasers are making the jump from potentially dangerous, but mostly annoying (laser pens aimed at cockpits of aircraft in flight) to a full-blown threat to aviation. It is possible to protect something against every other weapon. Every other weapon has some kind of guidance (such as a missile seeker that can be scrambled with a system like DIRCM), or is something physical that can either be stopped (traditional armor, like a tank) or intercepted (the bullet shooting a bullet theory).

Is there any way to stop a laser, besides mirrors I guess? I suppose something can be done in the realm of heat dissipative paint, but if a laser can burn through steel, that doesn't sound too promising. To me, at first glance anyway, it appears to be an 'I win button'.

You mentioned it, mirrors. What's wrong with reflectivity as a method to eliminate or reduce the impact of a laser beam?

It's a lot more difficult to stop or redirect many other non-guided projectiles like bullets.

Reflective coatings like mirrors work to a degree, but for extremely high beam energies they're still not a complete answer. A standard aluminium coating, for instance, is between 92% and perhaps 96% efficient at reflecting in the visible range, UV, and near IR. A 1 megawatt laser beam, therefore, would be mostly reflected, but still get through with between 40 and 80 kW of energy. This is more than enough to very rapidly vapourise the reflective coating, at which point it isn't a mirror anymore.

A dielectric coating can be made to reflect up to 99.9%+ of a specific frequency, but is very narrow-band, typically only a few nanometers wide so much be matched to the wavelength of the laser it's designed to reflect. The reflectivity drops off very fast either side of the reflective peak. They are also expensive and fragile, and applying a coating of this nature to an entire aircraft probably isn't even possible. Certainly not practical. It might be feasible to treat the windows.

However, it would still allow some energy through, 1 kW in the above example, which is still enough to cause damage, although much more slowly. Usually it will be the coating itself which is damaged.

The problem is exacerbated by the fact that weapons-grade lasers are not visible frequencies, but near to far IR. A CO2 laser, for example, is 10600nm wavelength, far outside the visible range. The Boeing ABL system uses an oxygen/iodine chemical laser which emits at around 1300nm, and the ground based solid state lasers are diode-pumped units that emit at around 1500nm.

The longer the wavelength of the laser, the less the beam expands over distance, so the laser spot on the target is smaller. This gives a very large energy density at the target, which makes the problems of reflecting the beam even harder.

In practice, reflective coating are most likely to be pretty ineffectual. You could, I suppose, gold-plate your missile or whatever, which would reflect most of the IR laser wavelengths with high efficiency, and rely on getting out of range fast enough to survive, but this brings a whole set of problems of it's own. Although you would have the prettiest high-speed bling around

An ablative paint is probably a better option. Something that will easily boil off under the beam irradiation, both absorbing a large amount of energy and ideally producing a vapour or plasma that reflects and/or absorbs the specific wavelength of the attacking laser. This effect is actually a problem when laser-cutting certain materials, so it should be possible to produce it on demand. The very high powers involved make it a difficult problem, but I suspect not an insoluble one.

Most of the laser weapons systems currently undergoing trials at the moment have very limited 'ammunition' or shot repetition rates, so in theory you don't need to hold off an incoming beam forever, just long enough for the other guy to overheat or run out of power or consumables.

For things like tanks, the problem is a little easier. It takes time for even a megawatt laser to burn holes in things, so thick heat conductive armor thermally insulated from the interior would probably help. Again, ablative coatings would ease the situation, and could be made much thicker on a tank than an aircraft. An aircraft by necessity has a very thin skin, a tank generally doesn't

You'd probably find in practice that the tactics called for firing at thin easily damaged bits like wheels and aerials, rather than punching holes through the side.

The existence of real energy weapons will certainly change the rules of the game though. At least until the other side gets them as well, which is inevitable. I expect a lot of research is ongoing to find a defence to the things.

pca

You could also try to confuse the aiming system, with a chaff or flare release or whatever, or by adopting a ducking and weaving flight pattern. For the time being, laser weapons will either need to stay aimed on you for a while if low-powered, or have a limited number of "shots" if high-powered. Either way, the aiming problem is already hard and the attacker can make it even harder.

Peter

Right now, my only real answer on how to fight the problem is to go after the aiming system. We currently have systems that can very rapidly detect, range, identify and pass off the targeting information to a weapon system just based on a single radar hit. Right now I think that and the tactics, techniques and procedures (TTPs) will be the only way to fight such a system.

It is a very scary thought.

No no no, you guys have got it all wrong. You have to modulate your shield frequencies. Everybody knows that.

PS: I totally have to give endgadget props for this illustration to go with the article. You can practically hear the artist going "pew pew pew mrrroooowwwrrrr kablam".