Talk:Kerr effect

Cubic crystals
Do all cubic structure crystals exhibit the Kerr optical effect? Since the Kerr effect can only occur in isotrophic(cubic) crystals, does it work the other way around? Also, what relation does the ferro, piezo, and pyroelectric effects have with the Kerr or Pockels effect, if any?


 * It's not true that the Kerr effect only occurs in cubic crystals. The Kerr effect is often used in polar liquids, for example. I had thought that all optical materials exhibited the Kerr effect to some degree, but I'm not so sure now. Hecht's book Optics at least implies that all isotropic media exhibit the Kerr effect.--Srleffler 23:47, 30 November 2005 (UTC)


 * Kerr effect take its origin in the (non-linear) polarization. The polarization is a function of the electric field. That field is well defined everywhere, even in empty space, so the polarization too. Meaning there could be Kerr effect everywhere. Note that in empty space, the electric susceptibility is zero, even non-linear term. So no Kerr effect in vacum :) —The preceding unsigned comment was added by Nicolas Bigaouette (talk • contribs) 15:58, October 6, 2006.
 * No, you are confusing polarization of electromagnetic waves and electrostatic polarization. Despite having the same name, they are not the same thing. The Kerr effect originates from nonlinear electrostatic polarization, which is a property of the medium not of the light.--Srleffler 19:51, 13 October 2006 (UTC)
 * No, I am not :) I was, like you, speaking of the polarization density. If you read carefully my post, you'll see that I never mension anything about the "electric field polarization". I said that the Kerr effect takes its origin in the "(non-linear) polarization". I could have added "via the nonlinear susceptibilities" to be more specific. This polarization really depends on the value of the electric field, as you can see here. You are rigth though about the "nonlinear electrostatic polarization being a property of the medium". Let me add that the polarization is a property of the medium, but it depends on the electric field. Nicolas Bigaouette 20:34, 16 October 2006 (UTC)

Kerr Constant
Do we know what the value of the kerr constant is? I didn't see it anywhere in the article.Strangealibi (talk) 13:04, 11 March 2008 (UTC)
 * The value is different for each material. It's a material constant, not a fundamental constant.--Srleffler (talk) 17:08, 11 March 2008 (UTC)

Symbol for scalar product (
dot product) should be a dot ·, not a colon :. Formula completely wrong? ===

For some reason, "Theory" uses ":" as

> The ":" symbol represents the scalar product between matrices.

That's a bit … strange, because the scalar product between matrices is otherwise called "dot product" for reasons of it typically being represented by a dot. Maybe this is a special convention in that field? Then again, as an EE with some background in that, I've never read that in a text book for physics students on the topic. So, hm.

But it's also strange, because in the formula

$$ \mathbf{P} = \varepsilon_0 \chi^{(1)} : \mathbf{E} + \cdots $$

the term $$\varepsilon_0 \chi^{(1)}$$ is not a matrix at all; it really makes no sense to call ":" an operator between matrices.

This undermines all my confidence in the presentation of this formula. It does not help that $$\mathbf P$$ should by notational convention describe a matrix (since bold), but if these $$:$$ are all scalar products, then all the summands on the right are scalars, and thus so is the sum. Marcusmueller ettus (talk) 10:36, 15 July 2023 (UTC)


 * There is such a thing as a "colon product," but it isn't necessarily needed here, and to say that it (the colon) represents a scalar product is wrong. I made some corrections to this ("DC Kerr Effect") section and added a couple of references. Dlinkhart (talk) 20:00, 17 November 2023 (UTC)