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

High-brightness laser lighting is emerging as a promising technology for next-generation illumination, projection displays, long-distance searchlights, automotive headlights, and other high-power lighting applications. Compared with conventional light-emitting diodes, laser diodes offer higher brightness, better directionality, and superior beam collimation. However, these advantages also bring a critical challenge: the highly focused blue laser beam generates intense irradiation and thermal loading on the color converter, often causing luminescence saturation, efficiency loss, color instability, and even thermal failure.

Phosphor-in-glass film (PiGF) color converters have attracted increasing attention because of their thin-film structure, simple preparation, low cost, and good compatibility with thermally conductive substrates. In a typical white laser lighting system, blue laser light excites the phosphor layer to generate yellow emission, which then mixes with residual blue light to produce white light. Nevertheless, conventional PiGF converters still suffer from insufficient blue-light absorption and optical loss at the film–substrate interface. A considerable portion of blue photons may pass through the phosphor layer without effective conversion, limiting luminous efficacy and increasing unnecessary heat accumulation.

To overcome these limitations, a team of material scientists led by Y. Peng from Huazhong University of Science and Technology developed a novel PiGF@sapphire color converter with a ZrO₂ microsphere-embedded reflector, referred to as PiGF@ZS. The core idea is to introduce a microstructured ZrO₂-in-glass reflecting interface between the PiGF layer and the sapphire substrate. This interface redirects unabsorbed blue photons back into the phosphor layer, extending their optical path and increasing the probability of absorption by YAG phosphor particles. As a result, more blue light is converted into useful yellow emission, while waste heat generation is reduced.

The team published their work in Journal of Advanced Ceramics on May 25, 2026.

“The key innovation of this work is not simply adding a reflective layer, but constructing a low-cost microstructured interface that simultaneously improves blue-light utilization and thermal management,” said Prof. Yang Peng, the corresponding author of the study. “This provides a practical route for developing high-efficiency color converters for high-power laser lighting.”

Experimental results confirmed the effectiveness of this opto-thermal design. Under 25 W laser excitation with a 5 mm spot diameter, the optimized PiGF@ZS converter achieved a high luminous efficacy of 240.5 lm/W and a maximum luminous flux of 3782 lm, demonstrating excellent resistance to luminescence saturation. Under 3 W excitation with a small 1 mm spot, PiGF@ZS delivered 1.2 times the luminous flux of the conventional PiGF@sapphire converter, highlighting the advantage of blue-light recycling under highly focused laser irradiation.

Thermal measurements further demonstrated the improved heat-management capability of PiGF@ZS. As the laser spot diameter increased from 1 mm to 5 mm, the thermal load was distributed over a larger excitation area, significantly reducing localized heat accumulation. Under 3 W excitation with a 5 mm spot, the surface temperature of PiGF@ZS decreased to 54.6℃, lower than the 61℃ measured for the conventional PiGF@sapphire converter. This reduced operating temperature is critical for maintaining stable optical output and extending device lifetime under high-power operation.

The team also assembled the PiGF@ZS converter into a white laser diode module and demonstrated its practical lighting performance in indoor and outdoor tests. The resulting laser lighting system showed strong beam collimation and long-distance illumination capability, indicating promising application potential in high-brightness field lighting, projection systems, automotive lighting, and special-purpose illumination.

Other contributors include Hongjin Zhang, Wei Cheng, Tao Lu, Jiuzhou Zhao, Xiaowei Liu from Huazhong University of Science and Technology, China.

About Author

Prof. Yang Peng is an Associate Professor and Ph.D. supervisor at Huazhong University of Science and Technology. He is an IEEE Senior Member and has been recognized as a Hubei Young Talent, Wuhan Talent Program awardee, and municipal-level innovation and entrepreneurship leading talent. His research focuses on advanced electronic manufacturing and semiconductor chip packaging integration, including luminescent glass-ceramic materials and device packaging, avionics devices and microsystem integration, power devices, and thermal management. In recent years, he has led multiple research projects, including the National Natural Science Foundation of China, sub-projects of the National Key R&D Program of China, the Hubei Key R&D Program, and the Hubei High-Quality Manufacturing Development Program. Prof. Yang has published more than 70 papers in journals such as Advanced Materials, Advanced Functional Materials, Laser & Photonics Reviews, IEEE Electron Device Letters, IEEE Transactions on Electron Devices, and Journal of Advanced Ceramics. His publications include three ESI highly cited papers and three cover papers, with over 2,500 Google Scholar citations and an H-index of 31. He has filed more than 40 Chinese invention patents and serves as a youth editorial board member, assistant editor, and guest editor for several academic journals. His research interests include electronic packaging and micro/nano manufacturing, aerospace electronic devices and microsystem integration, optoelectronic devices (LEDs/LDs) and opto-thermal regulation, MEMS devices, and reliability.

Funding

This work was supported by National Natural Science Foundation of China (52475594), Hubei Provincial Natural Science Foundation of China (2026AFC0612), Key Research and Development Program of Wuhan (2025050102030007), and Natural Science Foundation of Wuhan (2026040101030010). The authors would like to thank the Analytical and Testing Center of Huazhong University of Science and Technology for the support in PL, SEM, decay, DSC measurements.

DOI Link: https://doi.org/10.26599/JAC.2026.9221327

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2024 IF is 16.6, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508