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Forum: Processes Involving Optical Photons
Re: Question How to define the WLS quantum yield (vesna cuplov)
Re: Feedback Re: How to define the WLS quantum yield (Gumplinger Peter)
Date: 09 Jul, 2012
From: Sarah Eno <Sarah Eno>

I am also confused about this issue.

When I look at data shifts for WLS fibers, such as:

http://www.detectors.saint-gobain.com/uploadedFiles/SGdetectors/Documents/Brochures/Scintillating-Optical-Fibers-Brochure.pdf

second to bottom figures on page 6 (BCF-91A and BCF-92), for "absorption", there are unit-less numbers.

In the GEANT4 routine WLSABSLENGTH, this should be a number with units of length.

Do you multiply the absorption length of the binder (perhaps polystyrene) by the numbers in the figure on page 6 of the fiber data sheet linked above? How did you, for example, have other people gotten the values used in this routine?

Also, I wonder about the following: My understanding of the wavelength shifting process is from:

http://ac.els-cdn.com/0168583X96003187/1-s2.0-0168583X96003187-main.pdf?_tid=b4b9ba66741f5e77810b3c52e948520b&acdnat=1341857945_4162cf34f404c05982c215895a1d5101

I think this says that a photon is wave length shifted when the binder absorbs the photon, and the energy is transferred by non-radiative dipole-dipole interactions to excited levels of the solute, producing fluorescence. From this, I assume that the photon is absorbed by the binder, and then there is a probability of this non-radiative transfer, given by those figures in the saint-gobain brochure that do not have units of length, but look like probabilities (a "quantum efficiency"). This is why I think you multiply the binder absoption length by the numbers in this figure to get the numbers needed by your routine.

However, then I have a question: there are photons that are absorbed within the fiber, but that do not result in a wave-length shifted photons. In this case, I guess the absopbed photon's energy is dissipated through phonons or some other mechanism. How is this handled? Is there some other place where you put in the absorption length of the binder * (1- the quantum efficiency) to represent photons absorbed but not shifted?

Best Sarah Eno U. Maryland

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1 Feedback: Re: How to define the WLS quantum yield   (Gumplinger Peter - 10 Jul, 2012)
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