What happens when 2 beams of light interact?

[rgtr]

TL;DR

I was reading sometimes nothing happens when 2 beams of light interact but other times it can cause light to turn into other particles. What particles does the 2 light beams turn into?

I realize turn into probably isn't the correct term.

Also I know gravity can bend light but can gravity cause light to turn into other particles?

I am layman so can someone explain this in layman's term? Also I am not even sure the quantum section is the correct section.

 

[DrChinese]

Summary:: I was reading sometimes nothing happens when 2 beams of light interact but other times it can cause light to turn into other particles. What particles does the 2 light beams turn into?

I realize turn into probably isn't the correct term.

Also I know gravity can bend light but can gravity cause light to turn into other particles?

I am layman so can someone explain this in layman's term? Also I am not even sure the quantum section is the correct section.

Generally, 2 beams of light do not interact. When they do, they do not create particles other than light.

And gravity does not turn light into other particles. It is not clear that gravity is a quantum force, which would be necessary for that to ever be a consideration.

As a side note, it would be helpful to mention where you read that light "turns into other particles" so we would have some context. There are situations, for example, where energetic photons can interact with other particles yielding a variety of results.

 

[rgtr]

I assume no one knows what gravity is in quantum mechanics. Is my assumption correct?

But assuming gravity is quantum force how does this change the particle of light into other particles?

Also when do 2 light beams interact and what are the results? What is an energetic photon vs a photon?

 

[Dale]

And gravity does not turn light into other particles.

I think you can get electron-positron pair production for very high intensity and high energy beams.

 

[vanhees71]

As far as I know, it has not been observed directly yet, but in leading order QED perturbation theory of order $\alpha^2$ two photons can annihilate to an electron-positron pair. It's the time-reversed process of electron-positron annihilation to two photons.

At higher orders you can also have the elastic scattering of two photons (order $\alpha^4$). It's a set of one-loop diagrams with four electron-positron lines running around.