High-Quality Laser-Driven White Lighting Enabling by Collecting Backward Emission Light of Phosphor-in-Glass Film

Phosphor-in-glass film (PiGF) has been considered as a credible color converter in laser-driven white lighting. However, the PiGF confronts the inevitable roadblock of low light extraction efficiency, serious backward scattering, and low saturation threshold in transmissive configuration. In this work, a unique reflection design of heat-conducting PiGF-B converter was proposed for high-quality laser-driven white lighting. The PiGF-B converters with different film thicknesses and side lengths were excited by a blue laser diode (LD) and their optothermal performance was evaluated and compared with the traditional PiGF-T converter. Attributing to the backward emission light collection of mirror Al reflection cup and the high thermal conductivity of sapphire heat sink, the saturation power density and luminous flux threshold of PiGF-B-5 converter are 1925.3 lm and 15 W/mm2, which are over two times higher than the traditional PiGF-T-5 converter of 398.6 lm and 6 W/mm2, respectively. Furthermore, the PiGF-B-5 converter displays better correlated color temperature (CCT) and thermal stability even under higher power laser excitation. The results demonstrate that the PiGF-B converter provides an effective strategy for enabling high-quality laser-driven white lighting.