Message: Unexpected behavior of WLS fiber Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

Question Unexpected behavior of WLS fiber 

Forum: Processes Involving Optical Photons
Date: 21 Apr, 2013
From: Athreya Shankar <Athreya Shankar>

Hello all,

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

 Add Message Add Message
to: "Unexpected behavior of WLS fiber"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews