[[Mod. note -- I apologise for the delay in processing this article,
which the author posted on Saturday 2020-03-28.
-- jt]]
Jonathan Thornburg wrote:
Net Latham asked:
Has anyone ever measured any change in either frequency or wavelength
in a beam of light between its traversal of a material of refractive
index <= 1 and its further traversal of another material, one of
refractive index > 1?
In article <20200314174409.GA56566@iron.bkis-orchard.net>, I wrote
As for direct measurements, I suspect microwaves in waveguides or
coaxial cables would be the easiest. Measuring the speed & frequency
of EM waves in a coaxial cable is a standard upper-level undergraduate physics experiment (I've done it), and directly measuring the wavelength would just need adding cable taps at various points along the cable
to sample the passing EM field.
Ned Latham then asked
How did you deal with Total Internal Reflection?
and
Sample it, how?
Thank you for the replies to those questions, Jonothan. They involve a
matter related to this one, and I will be looking deeper into them later.
For the present though, what I'm interested in is whether experimenters
can meansure frequency of wavelength of light in optical cable (or a cable surrogate, like a 20m glass rod)?
[[Mod. note -- Optical frequencies can be measured using frequency combs.
This article
https://link.springer.com/chapter/10.1007/0-387-23791-7_7
looks like a review of the technique, but alas it's paywalled. :( :(
But, typing "optical frequency measurement" into scholar.google.com
returned just over 3 million results just now; many of which have
open-access copies available (look over in the right-hand column of
the google-scholar search results for links to open-access pdfs).
This Wikipedia article
https://en.wikipedia.org/wiki/Kerr_frequency_comb
describes generating optical frequency combs in various refractive media (silicon nitride, diamond, aluminum nitride, silicon).
Measuring the wavelength is relatively straightforward, just requiring
your favorite interferometer (Michelson, Fabry-Perot, Mach-Zehnder, etc.).
-- jt]]
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