Front-efficiency enhanced composite structure ceramic phosphor for high-power laser lighting and display applications

Composite ceramic phosphors are recognized as potential materials for laser-driven lighting and display applications due to their high luminous efficiency and excellent thermal stability. However, the substantial refractive index mismatch between ceramic and air reduces the forward light extraction efficiency. Meanwhile, thermal conduction pathways require further enhancement when irradiated at high-power blue laser. This paper proposed a composite structure phosphor combining composite ceramics (YAG/Al₂O₃-Ce:LuAG) with optical adhesive and glass lenses. The gradient of the above refractive index enhanced the light extraction in forward emission, as high as 24.5%, with the luminous efficiency reaching 231 lm/W. Thanks to the existence of the glass lens, the beam angle of the lighting source reduced from Lambertian distribution to 6.2°. Meanwhile, this architecture optimizes thermal management, withstanding 48.4 W/mm² blue laser irradiation without saturation while achieving 5196 lm of luminous flux under 28.1 W excitation. These results demonstrate that the proposed composite structure phosphor provided a solution to improve the front-efficiency for laser lighting and display application.