3
$\begingroup$

I first recall reading about such an effect in a SF story entitled "Rails Across the Galaxy" which involved self focusing laser beams. And in a science paper here

$\endgroup$
5
$\begingroup$

From your link's abstract:

We argue that long-range photon-photon attraction induced by the dipole interaction of two electron-positron loops can lead to “vacuum self-focusing” of very intense laser beams. The focusing angle θF is found to increase with the beam intensity I as θF∼I^4∕3; for the laser beams available at present or in the near future, θF≃10^−10 - 10^−7.

This is a very small angle, practically non measurable as they say in their conclusion:

Our calculation shows that the focussing effect is present even for the plane wave, for which the leading order contribution from the box diagram of Fig. 1(a) vanishes. The magnitude of the expected effect however makes its experimental observation challenging. In particular, in a realistic experimental setup it would have to be distinguished from the non–linear effects caused by the presence of the air.

Even in vacuum observing such small focusing will be hard, let alone using it for some purpose, imo.

$\endgroup$
2
  • $\begingroup$ I have a feeling this is not the final word on it. At the time (1982) I sort of recall seeing another paper that predicted a much larger effect. I am going to have to try and dig it out. The problem is, the only search terms I might use, "photon bunching" applies to a different phenomenon entirely $\endgroup$
    – user56903
    Jan 18 '15 at 21:12
  • $\begingroup$ the key words is "photon photon" interaction. It is very weak, because it has at least 4 electromagnetic vertices. Or "emergence of light from photons". There exists a paper but it just deals with linear cases. something like you wish for will be highly non linear . also "complexity and electromagnetic waves" $\endgroup$
    – anna v
    Jan 19 '15 at 5:52
0
$\begingroup$

Well if the experiment was performed in space the observation of such small focusing angles wouldn’t be very difficult. One would simply need to allow the beam a longer distance to propagate so as to see the effect. As for the angle being much less than the divergence of a “typical” laser beam this is merely a function of beam diameter. If (as proposed by Philip Lubin at UC Santa Barbra) an ordered array of phased lasers were constructed in space up to a few kilometers in diameter or so then the divergence angle of a beam such as that would be sufficiently small that the effect could perhaps be observed. .... Which of course does in fact open the door to at least the theoretical possibility of long distance divergenceless laser beam propagation in vacuum and thus power beaming over interstellar distances.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy