Canceling out-deflecting laser beams with each other?

[Sea Skimmer]

I was wondering if anyone had any ideas as to how effective it might be to block a laser beam with another identical laser beam intercepting roughly down the axis of the first beam. My understanding is while very slight, photons do affect each others paths of travel, so some kind of deflection should take place proportional to the amount the beams intersect. But I have no clue on just how signifcant that kind of effect could become if you had two high power lasers aimed at each other.

Its an idea I saw put forward as a possible laser weapons defense, and while it seems like it would work to burn up the enemy laser cannon on the other end, I’m skeptical that you could usefully disrupt or deflect a weapons grade, or any grade laser beam.

[Hamstray]

Wouldn't you have to know phase of the beam, or otherwise properties of it's photons you are trying to intercept? Doesn't the uncertainty principle apply?

[Kuroneko]

But I have no clue on just how signifcant that kind of effect could become if you had two high power lasers aimed at each other.

In a vacuum, there are two modes of interaction that can occur. One is through pair production, which won't happen unless the photons are extremely energetic, and the other is gravitationally. But while non-parallel beams do affect each others' trajectories gravitationally, this will be absolutely negligible for any reasonably realistic situation.

Outside a vacuum, there is also an opportunity for one beam to change the properties of whatever medium (e.g., air) enough to affect the propagation of the other beam, perhaps similarly to how inhomogeneously heated air can produce mirages through refraction. While I'm not sure how significant this would be (besides actually controlling it, the timeframe requirement may be too long), but it's definitely much more so than any other effect of passing another laser beam.

Wouldn't you have to know phase of the beam, or otherwise properties of it's photons you are trying to intercept?

Destructive interference doesn't get rid of the energy of the two beams.

[PaperJack]

Its an idea I saw put forward as a possible laser weapons defense, and while it seems like it would work to burn up the enemy laser cannon on the other end, I’m skeptical that you could usefully disrupt or deflect a weapons grade, or any grade laser beam.

The problem of laser weapons is that they have a straight line of fire: they can't fire beyond hills.
If the enemy is firing some kind of laser weapon, then it means you can see it directly and the best defense would be to shoot back.

[Sea Skimmer]

The problem of laser weapons is that they have a straight line of fire: they can't fire beyond hills.
If the enemy is firing some kind of laser weapon, then it means you can see it directly and the best defense would be to shoot back.

Counter battery is always a good defense. The trouble is, what if the enemy has a big long armored shroud around his laser beam optics on the ground, while the other laser is on an aircraft? Unless the enemy aims his beam right at the aircraft's own laser, that laser wont have LOS to return fire. The enemy laser might be burning the tail off the aircraft, while the aircraft's laser is having a much tougher time burning through that armored shroud to disable the laser optics. In this case counter battery may not work before the aircraft is already shot down. So if instead the aircraft could block or reduce the firepower of the enemy laser with its own laser, while diving for the deck to get out of the arc of fire, this could be a more effective defense then straight counter battery.

Other ideas might work for this too, like firing a laser seeking missile that releases laser obscurant dust down the track of the enemy laser beam, but being able to use your own laser is ideal since it would react much more quickly. That's why I'm interested in if the concept, suggested by others but seized on by me, could have any scientific validity. Its not sounding like direct interactions will work, but it may still be possible that a friendly laser could partly block an enemy laser through disrupting the air. Ill have to seek out additional sources of information, which is going to be hard since little real work is being done on laser countermeasures not not much of its is public domain.

[SpacedTeddyBear]

Well if you have a region of high optical intensity, you can produce Kerr Lens effect that alters the index of refraction of that region. I don't know how feasible it is outside of a lab let alone in atmosphere where compared to optical glasses, you have inhomogeneous distribution of molecules.

[Gil Hamilton]

Outside a vacuum, there is also an opportunity for one beam to change the properties of whatever medium (e.g., air) enough to affect the propagation of the other beam, perhaps similarly to how inhomogeneously heated air can produce mirages through refraction. While I'm not sure how significant this would be (besides actually controlling it, the timeframe requirement may be too long), but it's definitely much more so than any other effect of passing another laser beam.

I'm not sure using your laser to bend the path of another laser by refraction is that effective itself. Inferior mirages are only visible at very shallow angles (which is why you only see them on the crests of roads as you are driving) because even with a difference in the air close to a hot "surface" and colder air surrounding it, the difference in refractive index is still pretty tiny (for 589nm light, the nd20=1.000293, and that value approaches one as you raise the temperature and/or lower pressure). To deflect the beam passing through the inhomogenous hot regions of air significantly, I imagine you'd need a large path of really hot air to get the job done.