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After reading this post, I was left with the question of why bother with the luminescence--why not just collect the transmitted light with the fibers and transm

After reading this post, I was left with the question of why bother with the luminescence--why not just collect the transmitted light with the fibers and transmit it directly to the detector. The linked journal article makes it clear that the transmitted light is not collected by it entering the ends of the fibers. Instead, the transmitted light "scatters" off of the dye (changing wavelengths in the process), regardless of where and at what angle it hits the fiber, and some of it is scattered in the proper angular range to be transmitted along the fiber.

deleted 10y ago
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ISL 10y ago
Wavelength shifting should make the detector more effective. Most photodiodes prefer longer-wavelength photos. In addition, their goal with this project is to make it omni-directional, so capturing and coupling the incoming photons directly would be a challenge. There may also be a little bit of wavelength-dependent trickery, where green photons are better at staying coupled, but I'd have to dig more to decide.
mstresh 10y ago
Efficiently directing light into a fiber optic cable is a difficult problem, in general. The luminescence is their proposed solution to this problem and one of the key results in their journal article. You have to shine light end-on into a fiber--you can't couple light into the fiber by shining on it at the side. Even for large, visible-light scintillating fiber used in this paper, you only have a few degrees of possible incidence angles that direct the light into the fiber. See for example, (one of the first results from Google), the figure on page 4 of this datasheet [0]. [0] https://www.ethz.ch/content/dam/ethz/special-interest/phys/particle-physics/precisionphysicsatlowenergy-dam/TeachingContent/ASL/bicronfiber.pdf https://www.ethz.ch/content/dam/ethz/special-interest/phys/p...

deleted 10y ago

[deleted]

ISL 10y ago

Wavelength shifting should make the detector more effective. Most photodiodes prefer longer-wavelength photos. In addition, their goal with this project is to make it omni-directional, so capturing and coupling the incoming photons directly would be a challenge. There may also be a little bit of wavelength-dependent trickery, where green photons are better at staying coupled, but I'd have to dig more to decide.

mstresh 10y ago

Efficiently directing light into a fiber optic cable is a difficult problem, in general. The luminescence is their proposed solution to this problem and one of the key results in their journal article. You have to shine light end-on into a fiber--you can't couple light into the fiber by shining on it at the side. Even for large, visible-light scintillating fiber used in this paper, you only have a few degrees of possible incidence angles that direct the light into the fiber. See for example, (one of the first results from Google), the figure on page 4 of this datasheet [0]. [0] https://www.ethz.ch/content/dam/ethz/special-interest/phys/particle-physics/precisionphysicsatlowenergy-dam/TeachingContent/ASL/bicronfiber.pdf https://www.ethz.ch/content/dam/ethz/special-interest/phys/p...