|Message: Unexpected behavior of WLS fiber||Not Logged In (login)|
Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.
Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.
Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.
|1||0||1||no text / full text of posting|
|2||1||All||text for level 1 only / text for All postings|
Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.
|1||2||1||2 levels / 1 level (original posting)|
|2||3||2||3 levels / 2 levels|
|3||3||All||3 levels / all levels (all postings)|
I constructed a simple geometry where a wls fiber is placed within a plastic scintillator, and photons were generated from a point source in the center of the fiber. The fiber was symmetric with respect to the source, and a 100% efficient detector was placed at both ends of the fiber to count the number of trapped photons. The point source was monoenergetic, and was the energy was in the absoprtion range of the fiber, so as to simulate a situation wherein photons have just entered the fiber and are about to be wavelength shifted. I observed that, more than 90% of the photons got shifted, and only 10% of the wavelength shifted photons were trapped inside the fiber. This is expected, since total internal reflection comes into play only for a small fraction of the photons.
Next, I place an isotropic point source of same energy outside the fiber, in the middle of the scintillator. This is to see how many photons actually reach the fiber and get wavelength shifted. As expected, a lesser number get wavelength shifted, since not all the photons reach the fiber. However, double the number of wavelength shifted photons get trapped (around 15-20%). This is unexpected, since the trapping probability is intrinsic to the fiber and completely independent of the location of the source.
I would be grateful if someone could tell me where I am making a mistake, and if this is indeed what is expected.
Note: I have not given any explicit polarization to the source photons, since this would mean they are automatically assigned a correct random polarization.
Thanks in advance, Athreya