Facile fabrication of monolithic integrated YAG:Ce/Al₂O₃ ceramic modules with improved thermal management and optical performance for phosphor-converted laser lighting

To resolve the long-standing issues of thermal management, interfacial delamination, and efficiency loss in reflection-mode laser converters (such as phosphor-in-glass films and phosphor ceramic-substrate architectures), we developed a novel monolithic integrated ceramic (MIC) based on YAG:Ce, which eliminates the need for adhesives as well as the bonding interfaces formed by them and produces an inherently robust interfacial bonding with low thermal resistance and high delamination resistance. These modules were fabricated via a facile single-step solid-state reaction from bi-layered green pellets, consisting of an upper YAG:Ce phosphor layer and a lower alumina substrate layer. The integrated alumina substrate simultaneously performs three essential functions: robust mechanical support, efficient thermal management, and improved light reflection for the phosphor layer. This innovative design overcomes the interfacial bonding issue while optimizing both thermal and optical performance in a single cohesive structure. The saturation threshold, energy efficiency, and luminous exitance (spot confinement ability) of the as-prepared MIC modules were investigated using two testing modes, namely large-spot-mode (high laser power) and small-spot-mode (high laser power density). We validated and explained the critical role of phosphor layer thickness in light emission characteristics by evaluating its dependence on optoelectronic performance. These results conclusively demonstrate the MIC's exceptional capability for achieving ultra-high brightness and its potential for laser lighting applications.