Laser path regulation for high-saturation phosphor-in-glass film in high-brightness laser lighting

Laser diode (LD) lighting, as an emerging solid-state lighting technology, holds significant promise for obtaining high-power white light by exciting Y₃A_l5O₁₂:Ce³⁺ (YAG)-based phosphor-in-glass films (PiGFs). While optimizing materials and architectures of phosphor converters remains the primary approach for enhancing the saturation threshold, the influence of the laser path should not be overlooked. In this study, the optical performances of remote laser-excited light sources were effectively regulated by adjusting the laser incidence distance and angle between YAG PiGFs and blue LD. The results indicate that the threshold saturation improves with the increase of both incidence distance and angle. At a tilt angle of 51.4° and a distance of 107.5 mm, a high saturation threshold of 43 W and a luminous flux of 6527 lm were achieved, representing 2.5 and 2.3 times the values under the conditions of 0° and 92.7 mm, respectively. Furthermore, increasing the excitation distance and tilt angle significantly reduces the operating temperature of PiGFs, thereby enhancing their long-term operational stability. These opto-thermal improvements are the consequence of a reduced power density, which is caused by the enlarged spot area resulting from an increased excitation distance and angle. The findings demonstrate that the optimizing laser path can effectively enhance the optical performances of PiGFs, offering new perspectives for the packaging technology of white laser lighting sources.