Is it possible to create a higher energy photon from two lower ones?

In summary: The crystal does not need to pick up the difference in angular momenta, it only needs to provide the same energy and frequency.
  • #1
zrek
115
0
Is it possible for two photons to join their energy to structure a one photon of higher frequency?
join.png

Let's assume that the two incoming (IR) photons are prepared specially: coming in the same time, same wavelength, phase, appropriate (complementer) spins and angle, etc. They arrive the appropriate atom and giving the energy at the same time. The atom gets energized and releases one single photon (UV) with the double energy.

1. This is possible... OK, but why this is not happening in case of the photoelectric effect?
2. This is not possible, because of ... (the energy-time uncertainty?).

What do you think?
Thanks for the anwsers in advance.
 
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  • #2
No, it's not possible by conservation of angular momentum. The photon is spin-1, which ordinarily means that possible values for the spin along some axis (say, the z-axis) are +1, 0, and -1. Because it's massless, the longitudinal polarization state is forbidden and the z-component can only be +1 or -1. Hence, for two photons, the total z-component of angular momentum will be +2, 0, or -2. However, the outgoing photon will be +1 or -1. Hence, conservation of angular momentum would be violated by this process.
 
  • #3
LastOneStanding said:
No, it's not possible by conservation of angular momentum [...]

OK, and what is the difference if we are using a twophoton?

splitandjoin.png


I mean let's imagine an experiment when we split an IR photon to a twophoton and then we try to join them? Or it is also not possible? Is the photon splitting an irreversible process?
 
  • #5
fluidistic said:

Thank you, I have found this in the thread:
Vanadium 50 said:
A single photon cannot downshift to 2 because of something called Furry's Theorem. proved by Wendell Furry. This generalizes to any even number of photons.

If you have an odd number of photons, you will discover that spin-statistics sets all the amplitudes to zero: you end up with terms like the momentum of one photon dotted into the difference of the other two, which spin-statistics will force to be zero.

In matter, the premises of these arguments are no longer strictly true, and non-linear effects can produce them.

Am I understand well that if a special matter contributed, LastOneStanding's explanation about the spins is not always prevents the join?
 
  • #6
Due to angular momentum conservation the mentioned process is not possible in vacuum, but is probably possible in a medium.
 
  • #7
Demystifier said:
Due to angular momentum conservation the mentioned process is not possible in vacuum, but is probably possible in a medium.

Great, thank you. Please make it clear for me: if there is a lonely atom involved in the effect (like the case on the figure) is it count as a medium?
Would you be so kind and explain a little more how the spin problem is solved by a medium?
Thank you in advance.
 
  • #8
zrek said:
Great, thank you. Please make it clear for me: if there is a lonely atom involved in the effect (like the case on the figure) is it count as a medium?
In principle, yes.

zrek said:
Would you be so kind and explain a little more how the spin problem is solved by a medium?
The medium can take the missing angular momentum, so that the total angular momentum is conserved.

The process has still a very low probability (essentially because it typically requires a decrease of total entropy), but the time-inverted process - parametric down-conversion - is often produced in laboratories.
http://en.wikipedia.org/wiki/Parametric_down-conversion
In this case the medium is a nonlinear crystal.
 
  • #9
Very good, this is exactly what I was thinking about the problem, but I was uncertain.

Thank you very much!
 
  • #10
Demystifier said:
The medium can take the missing angular momentum, so that the total angular momentum is conserved.

The process has still a very low probability (essentially because it typically requires a decrease of total entropy), but the time-inverted process - parametric down-conversion - is often produced in laboratories.
http://en.wikipedia.org/wiki/Parametric_down-conversion
In this case the medium is a nonlinear crystal.

From the Wiki article: "A nonlinear crystal is used to split photons into pairs of photons that, in accordance with the law of conservation of energy, have combined energies and momenta equal to the energy and momentum of the original photon, are phase-matched in the frequency domain, and have correlated polarizations. (The state of the crystal is unchanged by the process.)"

Is this a mistake? How can the state of the crystal be unchanged when it needs to pick up the difference in angular momenta from the incoming and outgoing photons? I agree it must do—and obviously such processes due occur since down conversion with non-linear media is done regularly—but this seems at odds with the article. The citation for that paragraph is a book I don't have access to.
 
  • #11
I have an idea about it. Maybe one of the electrons in the shell of the medium atom changes its spin. The crystal (structure) itself remains unchanged (in avarage at least). Please correct me if I'm wrong.
 
  • #12
zrek said:
I have an idea about it. Maybe one of the electrons in the shell of the medium atom changes its spin. The crystal (structure) itself remains unchanged (in avarage at least). Please correct me if I'm wrong.

Well, that's what I assumed happens but then I would strongly dispute the wording that "The state of the crystal is unchanged by the process." The overall state of the crystal includes the spin states of its electrons.
 

FAQ: Is it possible to create a higher energy photon from two lower ones?

How is it possible to create a higher energy photon from two lower ones?

This is possible through a process called photon fusion, where two lower energy photons combine to form a single higher energy photon. This process requires extremely high energy and is only possible in certain conditions, such as in the core of stars or in particle accelerators.

What is the significance of creating higher energy photons?

Higher energy photons have the ability to penetrate deeper into matter and can be used for various applications, such as medical imaging, cancer treatment, and particle physics research. They also provide valuable insights into the nature of energy and matter.

Is creating a higher energy photon from two lower ones a common occurrence in nature?

No, this process is not common in nature and requires specific conditions and high energy levels. However, it does occur naturally in some astronomical events, such as the collision of two neutron stars.

What are the challenges in creating higher energy photons?

The main challenge is to provide enough energy to overcome the binding energy of the individual photons. This requires advanced technology and extremely high energy levels, which can be difficult and expensive to achieve.

Can creating higher energy photons lead to the production of new particles?

Yes, when two photons fuse to form a higher energy one, the excess energy can be converted into new particles, such as electron-positron pairs. This process is studied in particle accelerators, where high energy photon collisions can produce a variety of new particles.

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