Experiment
Two types of phosphor were applied to an SPE-based white LED package and analyzed for light output and color properties. In the first part of the study, YAG:Ce was characterized as a single layer and as two stacked layers. In the second part, YAG:Ce and a red phosphor (λp~615nm), were characterized as a single layer mixture and as two stacked layers in alternate orders. Experimental results were compared with optical ray-tracing and theoretical analysis. Light output and spectral power distributions were measured in an integrating sphere with a spectrometer. Optical ray-tracing was carried out in LightTools following a method used previously.8 A theoretical analysis of the light interaction with the phosphor layers was conducted following the method used in [9].