Achieving High Light Uniformity Laser-driven White Lighting Source by Introducing Secondary Phases in Phosphor Converters

Laser-driven white lighting sources have great potential for applications with super-high brightness, high directionality and long distance illumination, but are usually limited by their poor uniformity due to mismatch between blue laser light and phosphor converted light. In this work, a secondary phase of TiO2, BN, Al2O3 or SiO2 was introduced as scattering media in the Y3Al3O12 : Ce3+ (YAG) phosphor-in-glass (PiG) film to regulate the light path, where the optimum concentration of the secondary phase was determined, respectively. The images of illumination and speckle, angular distributions of luminance and color temperature, as well as optical properties of the white light produced by the different secondary phases based-YAG PiG films were investigated. The light uniformity in luminance and color temperature is greatly improved by introducing secondary phases, among which TiO2 is demonstrated as the best one as it has the largest relative reflective index. In addition, the YAG-TiO2 PiG film has the largest luminance saturation threshold of 20.12 W/mm(2) and the highest luminous flux of 1056.6 lm under blue laser irradiation. This work paves an avenue to choose appropriate scattering media in PiG films for realizing more uniform and brighter laser-driven white lighting source.