Talk:Nonlinear optics

message: 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)
thread_title:  Brillouin and Raman nonlinear? 

message: 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)
replies: text: Wrt was not beautiful, but at least correct. Your "correction" was wrong. Han-Kwang (talk) 11:33, 26 Dec 2004 (UTC)
thread_title: remark

message: Could please someone in the know add a section explaining the phenomenon from the quantum standpoint, i.e. some lower-energy photons come in, some (lower number) of higher energy photons come out. Explain the effect that produces these higher energy photons.
I am curious myself, and I believe that it would be a generally valuable addition. Thanks!
=ec 195.212.29.188 (talk) 10:14, 15 February 2011 (UTC)
replies: text: Interesting question.  As well as I know it (maybe not very well), the usual case doesn't depend on quantum properties of photons, but does depend on quantum properties of atomic electrons. The atoms are in the electric field of the incoming light wave, which has a wavelength much larger than the atoms. The electric field, as the article notes, is comparable to the electric fields that hold the atom together.  The reason that linear optics is linear (lucky us) is that at more ordinary intensities, the fields are small compared to those holding the electrons in their orbitals, and the (small) shifts are linear to a good approximation.  A (classical) electric field of E0sin(ωt) comes in, a non-linear effect generates the third harmonic  E1sin(3ωt). Just as classical as a mixer diode in a microwave receiver.  (No second harmonic by symmetry.)  This is in the limit of large numbers of photons, such that classical approximations work.   Gah4 (talk) 21:20, 15 November 2016 (UTC)
thread_title:  Quantum explanation 

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thread_title:  External links modified 

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thread_title:  External links modified 

message: I noticed the removal of a See also for lasers, which is probably right.  But then I considered that one for phase conjugate optics might be included, but there is no such page!  Should there be a page for phase conjugate optics?  It seems to me that it is important enough to have its own page, not just a section in this page. (Not that I feel qualified to write one.) Gah4 (talk) 21:23, 15 November 2016 (UTC)
replies: text: important question 188.189.5.151 (talk) 19:00, 13 February 2024 (UTC)
thread_title:  Phase conjugate optics 

message: Hi folks, I'm not sure if the very last line of this calculation is correct:
:\begin{align}
\mathbf{P}^\text{NL} = \varepsilon_0 \chi^{(2)} \mathbf{E}^2(t)
 &= \frac{\varepsilon_0}{4} \chi^{(2)} \Big[|E_1|^2 e^{-i2\omega_1 t} + |E_2|^2 e^{-i2\omega_2 t}\\
 &\qquad + 2E_1 E_2 e^{-i(\omega_1 + \omega_2)t}\\
 &\qquad + 2E_1 E_2^* e^{-i(\omega_1 - \omega_2)t}\\
 &\qquad + \left(|E_1|^2+|E_2|^2\right)e^{0} + \text{c.c.}\Big],
\end{align}
According to my calculations, there is a factor of 2 missing in front of :\begin{align}
\left(|E_1|^2+|E_2|^2\right)e^{0}
\end{align}  — Preceding unsigned comment added by 92.208.178.25 (talk) 19:14, 13 December 2017 (UTC)
thread_title:  Wrong calculation?