ABSTRACT Underwater laser‐driven lighting is limited by the poor heat dissipation of color converters, which causes luminance saturation and prevents miniaturization. This study presents a direct water thermal exchange method, allowing both the color converter and laser diode to dissipate heat directly into the surrounding water. A water‐contact green‐emitting Y 3 (Al,Ga) 5 O 12 :Ce 3+ (YAGG:Ce 3+ ) phosphor‐in‐glass (PiG) with a sandwich waterproof structure (SW‐PiG) was thus developed as the color converter, maintaining 89% of its luminous intensity even after 40 days of immersion in 80°C seawater. The SW‐PiG achieved an underwater illuminance of 2.5 × 10 5 lux at 15 cm under blue laser excitation, which is 14 times higher than that of a conventional heatsink‐based setup (1.8 × 10 4 lux). Notably, no luminescence saturation was observed even at 25 W laser excitation, while the conventional setup suffered thermal rupture at just 3.5 W. Finally, a miniature, super‐bright green light source was demonstrated, highlighting its potential to improve personal diving safety and enable wide‐area (60° divergence angle, >40 meters) underwater point‐to‐multipoint broadcast communication across diverse applications.
Wang et al. (Thu,) studied this question.