A novel PiGF@ZS color converter with a ZrO₂ microsphere-embedded reflector for high-brightness laser lighting

Luminescence saturation of static color converters represents a pivotal hurdle for the progression of next-generation high-brightness laser lighting. The conventional phosphor-in-glass film (PiGF) color converter faces inherent limitations in achieving high luminous efficacy (LE), constrained by insufficient phosphor excitation under focused laser irradiation and optical losses at the film-substrate boundary. Herein, a novel PiGF@sapphire (PiGF@S) converter with a ZrO₂ microsphere-embedded reflector (PiGF@ZS) was proposed for laser lighting. This designed microstructure effectively reflects unabsorbed blue light back to the phosphor layer, significantly enhancing light utilization efficiency and LE for high-power laser lighting. Furthermore, the effects of laser spot diameters on the luminescence saturation were investigated in the PiGF@ZS converter. Benefiting from this synergistic opto-thermal design, the optimized PiGF@ZS converter exhibits a high LE of 240.5 lm/W and a maximum luminous flux (LF) of 3782 lm at a 25 W laser (5 mm spot). Notably, under a 3 W laser with a spot diameter of 1 mm, the PiGF@ZS converter achieves an LF 1.2 times that of a conventional PiGF@S converter. Owing to the enlarged excitation area and improved heat dissipation, the PiGF@ZS converter achieves a lower surface temperature of 54.6 °C under a 3 W laser with a 5 mm spot compared with 61 °C for the PiGF@S converter, demonstrating enhanced thermal management capability. The microstructured ZrO₂ interface effectively mitigates thermal accumulation and enhances blue light utilization efficiency for PiGF-based laser lighting.