The progress toward developing a technique for the underwater remote detection of gases using Raman lidar is reported. In this work, we describe the development of the marine Raman lidar system for monitoring the CH4 gas of Taketomi submarine hot spring. The transmitter of lidar system was the third harmonic of a standard Q-switched Nd:YAG laser (355 nm). The receiver of this system consisted by a telescope with a diameter of 200 mm, a spectrometer, a CCD camera for measuring Raman spectrum, and a PMT for monitoring Raman lidar signals. In order to evaluate the performance of our system, we demonstrated the Raman spectroscopic measurements from a barge down to the water depth of about 30 m.

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T. Somekawa, S. Kurahashi, J. Kawanaka, and M. Fujita, "Development of the marine Raman lidar system," Proc. SPIE 10791, Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing XIV, 1079104 (Presented at SPIE Remote Sensing: September 11, 2018; Published: 9 October 2018); https://doi.org/10.1117/12.2324955.