How Do Two Explanations of Spatial Hole Burning Differ?

[Niles]

Hi

I am reading about spatial hole burning in the litterature, and I have come across two different explanations. I can't quite see how they relate to each other. Here they are:

1) In this explanation one uses the fact that in a linear cavity the optical field is a superposition of two counter-propagating waves such that they produce a standing wave in the medium. This will deplete the gain in all the nodes of the standing wave pattern.

2) In this explanation one simply says that e.g. TEM00 will saturate the gain in the medium in a TEM00-pattern.

As far as I can tell, these two explanations are not identical. Intuitively I would say the second one is the one that makes most sense, but the first one is mentioned in most books. Can someone shed some light on this matter?

Any help is appreciated.


Niles.

 

[marcelnv]

Hi there,
Was also looking for information on spatial hole burning. I how ever see a little rapport between the two explanations you provided.
In the first, the gain medium is linear and the waves traveling in opposite directions superpose to form standing waves. This causes depletion of the gain medium in all nodes of the standing wave. Right! But ask yourself what happens at the anti nodes?
Actually in standing waves, nodes are non vibrating points, so these parts of the gain medium are not seen by the laser light, there are wasted, so that the anti nodes on the other hand are much more busy or saturated if you want.
As for the TEM00 modes, I think since the number of the nodes depend on the wavelength, L=n\frac{\lambda}{2}, where L is the optical cavity length, some particular modes will be favored, in this case the fundamental mode of the laser.

That's about all I can say for now.