Characterization of 466 nm DFB Laser Diode for Underwater FMCW LiDAR Applications

Light detection and sensing (LiDAR) has emerged as a promising tool for underwater positioning and surveying, particularly in the context of unmanned underwater vehicles for ocean infrastructural monitoring. Frequency-modulated continuous wave (FMCW) LiDAR has advantages over time-of-flight (ToF) LiDAR, in terms of high sensitivity, speed detectability, and robustness across multiple devices. Regarding the light source, distributed feedback (DFB) lasers have considerable potential in terms of single-mode operation, frequency tunability, and the factors of size, weight, and power (SWaP). However, the practical DFB light source of a blue-green light that is water-transparent has been challenging to achieve so far. In this study, we characterized the frequency modulation depth and the frequency noise of the GaN-based DFB laser diode (LD) at 466 nm, which has been recently developed by Nichia Cooperation in Tokushima, Japan.