Diffusion of light in white LEDs

Energy efficient generation of white light has become an important societal issue in recent years. The technology of white-light emitting diodes (LEDs) is one of the main directions. Key challenges in the white LED usage are understanding scattering, absorption and emission from ab-initio, and extracting the transport properties in the region where both emission and absorption overlap. Physical understanding of multiple light scattering in the LED provides tools to extract optical parameters of this system, and greatly simplify the LED design process. In this work we have been able to measure the total transmission, using a novel technique, in the region where emission and absorption overlap, and to extract transport parameters in the whole visible range. 
We have studied transport of light in the wavelength range 400 to 700 nm, through polycarbonate diffuser plates with different phosphor concentrations of YAG:Ce3+ , that are used for commercial LEDs. We have developed a new technique to measure light transport of LEDs in the range where emission and absorption overlap. A narrow band light source is employed to measure the total transmission. In this case we observe a clear separation in wavelength between transmitted and re-emitted signals. We have therefore managed to extract the total transmission in the overlap region. These data allow us to deduce the lab in the previously inaccessible overlap region. We have managed to extract the full range of transport parameters for phosphor plates in the visible wavelength range using nanophotonic theory.