Achieving Ultra-Brightness Green Light Source with Electro-optical Conversion Efficiency up to 26.3% for Underwater Wireless Optical Communication

Abstract

Using blue lasers to excite green-emitting phosphors offers a compelling solution to address the “green gap” issue, providing a high-brightness green light source for underwater wireless optical communication (UWOC). However, current green-emitting phosphors show poor light conversion efficiencies or inadequate luminance saturation thresholds, impeding the development of brighter green light sources. Herein, the porous Lu₃Al₅O₁₂:Ce phosphor ceramics are designed, which shows no change in quantum efficiency (82%) even after 6000 h of extended aging. This design results in a substantial improvement in light conversion efficiency (61.6%), luminous efficacy (286 lm·W⁻¹), and an exceptional luminance saturation threshold of 33 W·mm⁻², culminating in a maximum green light flux of 4720 lm. Moreover, the high-directionality green light source device has been fabricated that achieves an illuminance of 6081 lx at a distance of 10 meters (15.0 W blue laser irradiation) with the electro-optical conversion efficiency up to 26.3%, much higher than that using green laser directly (usually <20%). This setup enables long-range underwater transmission of 65.3 meters with a peak data rate of 3.45 MHz, opening up new avenues for innovative advancements in UWOC technology.