Modeling of ceramic phosphor assemblies for high luminance solid state lighting

Cerium doped garnet ceramics enable laser pumped phosphor light sources with luminances above 1000 cd/mm². Design and function of such light sources is based on proper absorption and conversion together with customized scatter properties of the active material. Since a minor but relevant portion of the incident blue laser light is transferred into heat, proper thermal management is also indispensable. For calculation of key features such as possible luminous flux, CCT, dissipated heat, and more, numerical modeling is used. We present a finite element model for simultaneous calculation of heat and light generation and diffusion within the phosphor, and for the heat dissipation towards the heatsink on which the active phosphor is mounted. For this, light transport is described via the delta-P1 approximation, simultaneously for the exciting blue radiation and for the converted radiation. We present examples for modeling of the phosphor assembly, enabling insights impossible for experimental approaches. In particular, we look at the mechanisms of irradiance limitation, visualizing temperature distributions within the components, and demonstrate the predictive power of the model.