Laser-Driven High-Brightness Green Light for Underwater Wireless Optical Communication

Green light is generally used as the transmitter of underwater wireless optical communication (UWOC) system, but the currently available light-emitting diode (LED)-based green light has a poor luminous flux density (i.e., low brightness) and a low wall-plug efficiency (WPE), known as the “green gap”. In this work, it is proposed to produce the laser-driven green light by using blue laser diodes to pump the narrow-band green-emitting β-Sialon phosphor-in-glass (PiG) film. The dominant wavelength of the laser-driven green light can be tuned in the range of ≈520–540 nm, required for UWOC, by controlling the phosphor content at ≈60–80% and the film thickness at ≈150–185 µm. By introducing highly reflective TiO 2 into the PiG film, the laser-driven green light exhibits a maximum luminous flux density of 1260 lm mm −2 under blue laser excitation with a power density of 15.49 W mm −2 . For UWOC application, the green light is demonstrated to have a modulation bandwidth of 1.76 MHz, a high WPE of 8.7%, and a long transmission distance of ≈61.6 m. This work suggests that the laser-driven high-brightness green light will be a promising light source for UWOC.