Optothermal Performances Investigation of Phosphor-Converted White LDs With Alumina Substrate-Based PiGF Converters

Phosphor-in-glass film (PiGF)-based phosphor-converted white laser diode (pc-WLD) is regarded as a potential high-brightness white lighting source. For reflective PiGF converters, the optothermal performances are particularly related to heat dissipation efficiency, mainly depend on the heat-conducting substrate and extra heat dissipation method. In this article, we prepared PiGF-Al2O3 substrate (PiGF-AS) converters by coating and sintering LSN:Ce phosphor glass film directly on Al2O3 substrates to slash thermal conduction resistance. The other factors that significantly impact heat dissipation efficiency—substrate size (area and thickness) and the presence or absence of heat sink—are extensively evaluated in the PiGF-AS-based pc-WLD. It is delightful to find that both the optical performance and reliability of PiGF-AS could be improved by expanding the substrate area, increasing substrate thickness, and combining the heat sink. The PiGF-AS achieves a maximum luminous flux (LF) of 1564 lm under a laser power density of 12.36 W/mm2. The PiGF-AS-based pc-WLD with $5\times 5\times0.5$ mm3 Al2O3 substrate realizes cool white lighting with a correlated color temperature (CCT) of 4918 K and a chromaticity coordinate of (0.3440, 0.3592). Furthermore, the working temperature of PiGF-AS is reduced by the heat sink from 218 °C to 58.3 °C (~73.1%) under a 3.18-W/mm2 laser. The results show that the prepared PiGF-AS-based pc-WLD shows excellent optothermal performances and great potential in white laser lighting. Meanwhile, this work provides a reference for the high heat-dissipation packaging design of PiGF-based pc-WLD.