Ceramic phosphor wheels for high luminance SSL-light sources with >500W of laser power for digital projection

Lighting applications that require luminance levels above several 100 cd/mm² cannot be addressed with LEDs today. Laser pumped phosphor (LPP) light sources are an emerging technology that helps to address this field with solid state lighting (SSL). Digital projectors with a LPP light source are already commercially available. They make use of phosphor wheels that are irradiated with blue laser light to generate light via photo-luminescence. The power limit of the phosphor wheel is determined by the peak temperature of the phosphor at the laser spot. We present experimental and numerical studies on the temperature contribution of both, the wheel geometry and the phosphor material, and show that ceramic phosphor rings are the best choice for high power and high luminance applications. Results for power levels close to 700W and an irradiance above 180 W/mm² are presented.