Researchers improve light propagation analysis tools for better white LEDs
Investigating the transport of light through slabs that scatter and strongly absorb light (like a mix of phosphors spread over a blue emitter to create white light), the researchers claim their numerical method circumvents the main bottleneck of conventional numerical methods, providing a 17-fold speed up in computational time with the same error, accurately describing the light that stays inside the LED by absorption and scattering.
What makes good prediction particularly difficult, according to the authors is that some of the light is absorbed, but re-emitted in another colour. One way is trying to define all possible light rays, and use a lot of computing time to get a result, but this doesn’t give much insight in what is actually happening.
red is the new method, black is a numerical
‘Monte Carlo’ check.
The researchers have built a setup to collect all the light around the phosphor plates, in the whole visual spectrum to deduce the actual absorption and scattering using the radiative transfer equation, well known in astronomy.
This results in a full description of light propagation inside and outside the phosphor plates. Compared to a description using diffusion theory, the absorption level is up to 30 percent higher. At the same time, the method is about 17 times faster than the numerical approach.
The research has been done in the Complex Photonic Systems group of UT’s MESA+ Institute for Nanotechnology, together with Philips Lighting in Eindhoven.
University of Twente – www.utwente.nl/en/
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