High‐Performance 535‐nm Green Laser Diode Enabling Free‐Space and Underwater Optical Links

There is a continuous growing demand for visible light communication (VLC) with high‐speed and low‐latency in both free‐space and underwater environments. However, green laser diodes (LDs) remain constrained by the long‐standing “green gap”, where material quality and device structure challenges limit their luminous efficiency and communication performance. Herein, we demonstrate a GaN‐based green LD emitting at 535 nm, incorporating InGaN multiple quantum wells with graded InGaN quantum barriers. Strikingly, the device achieves a light output power over 650 mW, a threshold current density of 2.6 kA/cm 2 , a narrow optical spectrum with a full width at half maximum of 3.4 nm, together with a wall‐plug efficiency above 6%, while maintaining excellent operational stability with only 7.74% power degradation after 960 h continuous‐wave operation. With a −3 dB modulation bandwidth over 1.3 GHz, the LD enables high‐speed data transmission, achieving data rates of 12.36 Gbps in free space and 8 Gbps in underwater environments using discrete multitone modulation. These results represent a significant advancement in overcoming the “green gap” and establish a promising platform for high‐performance GaN‐based visible light LDs in next‐generation high‐speed VLC systems.