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

Abstract

AbstractGreen 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 TiO2 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.