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I just stumbled upon this question.

For massive particles like an electron, it is easy to make them follow a non-geodesic path by applying an external force. In case of the electron, one can put it under some electric field so it undergoes accelerated motion.

I wonder if it is possible to make massless particles like photons follow a non-geodesic path. I think the simplest way is to send a light beam into a diamond. Will it work?

Qmechanic
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Jimmy Yang
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2 Answers2

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A diamond would be very expensive. A mirror would be cheaper solution.

Fred. Zwarts
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2

I think, yes, it is possible to influence the geodesic path of a photon. And if I have understood the question correctly, then preferably without reflection on or absorption/re-emission in a material medium.

Since the photon is simultaneously an electric and a magnetic dipole and these fields periodically change their orientation, it would make sense to use an external E or B field to exert an influence. This field would have to oscillate just as quickly as the frequency of the photon. Then we could achieve an attractive effect. Technically, however, we do not have this possibility.

The solution lies where Michael Faraday already experimented, the polarization of light in a magnetic field - it also works with an electric field. If I set up helically aligned magnetic fields along the geodesic path of the light, then I rotate the direction of polarization of the photon continuously. This should not only make it possible to deviate from the path, but also to split out light of different wavelengths.

HolgerFiedler
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