Investigation of Laser-Induced Luminescence Saturation in a Single-Crystal YAG:Ce Phosphor: Towards Unique Architecture, High Saturation Threshold, and High-Brightness Laser-Driven White Lighting

A significant obstacle in the development of phosphor-converted white-laser diodes (pc-wLDs) is associated with the laser-induced luminescence saturation of phosphors. YAG:Ce is a canonical yellow-emitting phosphor. However, there has been few systematic research of measurement and understanding of the luminescence saturation in YAG:Ce yet. Here, we analyze the luminescence saturation of a single-crystal YAG:Ce with a unique phosphor geometry. A novel characterization method, which enables the optical signals to be fully collected and analyzed, is introduced. The effects of both laser power and laser power density on the luminescence properties and colorimetric properties of the YAG:Ce are studied systematically. The results show that a single-crystal YAG:Ce has a high saturation threshold (over 360 W/mm2) so that only a very slight saturation behavior can be observed at a high power density. Furthermore, a pc-wLDs light source based on the combination of a single laser diode and a YAG:Ce phosphor exhibits remarkable efficiency and stability. Under the excitation of a 3.38 W blue laser (~100 W/mm²), the white light emission with the luminous flux of 465 lm, the luminous efficacy (LE) of 145 lm/W, and the correlated color temperature (CCT) of 4980 K can be achieved.