Talk:Nonlinear optics
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Should the processes under "related processes" be listed here at all? I'm not completely sure about Raman. I believe that the Raman-shifted "fluorescence" intensity is linear in excitation intensity, on the other hand it is a chi3 process. Stimulated Raman is of course a different story.
Would anyone (DrBob?) care to write a few words about phase conjugation? -- Hankwang 09:40, 4 Mar 2004 (UTC)
- It's true that the "related processes" are not strictly speaking part of nonlinear optics, but they are almost always covered under that title in textbooks and courses. Perhaps just keep them as brief mentions here, and put their descriptions in seperate articles.
- Phase conjugation can be achieved by both four-wave mixing and stimulated Brillouin scattering, so its kind of hard to place. I'll see if I can write a brief overview soon. -- DrBob
Brillouin and Raman nonlinear?
Rpaschotta moved Brillouin and Raman scattering from "related processes". Nonlinearity w.r.t. the light intensity suggests that the Raman- or Brillouin-shifted peak would increase disproportionally with increasing laser intensity. AFAIK that is not what happens in typical applications. I graduated on a project involving Brillouin scattering on GHz phonons and did a PhD in time-resolved spectroscopy and it is not obvious to me, so maybe it's a good idea if Rpaschotta wrote a few words about why it classifies as nonlinear spectroscopy.
Han-Kwang (talk) 14:08, 25 Oct 2004 (UTC)
Ok, here are some remarks. Of course, the Brillouin shift doesn't depend on intensity. Nevertheless, the interaction is nonlinear in the involved optical fields. Consider e.g. two beams interacting in a Raman-active medium. Now reduce both powers by a factor of ten. The result will NOT just lead to ten times lower output intensities of both beams. Instead, the interaction will become weaker. This is clearly different to the case of an electro-optic modulator, where the optical output depends linearly on the optical input (within certain bounds, of course).
RPaschotta 12:05, 30 Oct 2004 (UTC)
Hmm, I see what you mean. But along the same lines you could defend that Beer-law absorption is a nonlinear process because in a pump-probe experiment the signal depends on both the pump pulse and the probe pulse. Unless you talk about specific applications, both Brillouin and Raman spectroscopy only involve one optical field, on which the signal depends linearly.
Han-Kwang (talk) 15:58, 30 Oct 2004 (UTC)
remark
Why do scientists use the stupid phrase "with respect to" (which they must acronymise to w.r.t. or wrt) instead of "about" or "from"? lysdexia 01:10, 21 Dec 2004 (UTC)