Spot phosphor concept applied to a remote phosphor light-emitting diode light engine

Abstract

Although remote phosphor technology outperforms conformal phosphor technology for midpower applications, one of the limiting factors due to its impact on the total cost is the amount of phosphor required. Furthermore, an important loss mechanism in remote phosphor light-emitting diode (LED) technology is the reabsorption of recycled, downconverted light by the phosphor. An obvious solution to this issue is to enable a light path for the converted light, such that further interactions with the phosphor element are avoided. We propose a spot phosphor concept to achieve this goal. To explore this configuration, a simulation model of a phosphor element is devised and validated. The optical input parameters are based on experimental data and the application of the inverse adding-doubling method. The resulting configuration, along with a long-pass filter, is shown to be a potential solution for reduction of phosphor usage. The moderate decrease in the light extraction ratio (LER) when applying the spot concept is partly attributed to the losses in the secondary optics needed to narrow the LED beam; the combination of the spot concept configuration with a directional light source such as a laser diode is shown to be a powerful combination for the enhancement of the LER.