Reflective Phosphor-in-Glass Color Converter for Laser-Driven White Lighting

In this work, we fabricated a phosphor-in-glass (PiG) film on Al-coated sapphire as reflective color converter driven by a laser diode. The borosilicate glass PiG film was sintered on heat-conducting sapphire and an Al thin layer with high reflectivity was deposited on the other surface of the sapphire, providing the function of heat dissipation and light reflection. The optical performance of the laser-driven white emitter (LD-WE) was adjusted by controlling the PiG film thickness. At a thickness of 120 μm, the LD-WE emits white light with a correlated color temperature (CCT) of 6733 K and a chromaticity coordinate of (0.3104, 0.3184). When the laser power increases from 0.32 to 1.12 W, the luminous flux increases from 19.3 to 129 lm and the light quality is stable. The color rendering index (CRI) of LD-WE reaches 82.5 by adding red phosphor. Furthermore, the converter has low working temperature from 30.7 to 45.6°C due to the effective heat transfer of sapphire.