[1] [1] Chong Z R, Yang S H B, Babu P, et al. Review of natural gas hydrates as an energy resource: Prospects and challenges [J]. Applied Energy, 2016, 162: 1633-1652.

[2] [2] Veluswamy H P, Wong A J H, Babu P, et al. Rapid methane hydrate formation to develop a cost effective large scale energy storage system [J]. Chemical Engineering Journal, 2016, 290: 161-173.

[3] [3] Zuo R Q, Li Y. The research and successful production test for NGH in Alaska north slope, USA [J]. Exploration Engineering (Rock & Soil Drilling and Tunneling), 2017, 44(10): 1-17.

[4] [4] Liu C L, Meng Q G, He X L, et al. Comparison of the characteristics for natural gas hydrate recovered from marine and terrestrial areas in China [J]. Journal of Geochemical Exploration, 2015, 152: 67-74.

[5] [5] Baer D S, Paul J B, Gupta M, et al. Sensitive absorption measurements in the near-infrared region using off-axis integrated cavity output spectroscopy [C]. Proceedings of SPIE, 2002, 4817: 167-176.

[6] [6] Sanders V. High-precision reflectivity measurement technique for low-loss laser mirrors [J]. Applied Optics, 1977, 16(1): 19-20.

[7] [7] O’Keefe A, Deacon D A G. Cavity ring-down optical spectrometer for absorption measurements using pulsed laser sources [J]. Review of Scientific Instruments, 1988, 59(12): 2544-2551.

[8] [8] Engeln R, Berden G, Peeters R, et al. Cavity enhanced absorption and cavity enhanced magnetic rotation spectroscopy [J]. Review of Scientific Instruments, 1998, 69(11): 3763-3769.

[9] [9] Paul J B, Lapson L, Anderson J G. Ultrasensitive absorption spectroscopy with a high-finesse optical cavity and off-axis alignment [J]. Applied Optics, 2001, 40(27): 4904-4910.

[10] [10] Tian X, Cao Y, Wang J J, et al. High sensitivity detection of two-component CH4/H2O based on off-axis cavity enhanced absorption spectroscopy [J]. Spectroscopy and Spectral Analysis, 2019, 39(10): 3078-3083.

[11] [11] Dong Y, Wang J J, Zhou X Y, et al. Detection of methane hydrate in deep sea based on off-axis integrated cavity output spectroscopy [J]. Chinese Journal of Lasers, 2020, 47(8): 0811003.

[12] [12] Gonzalez-Valencia R, Magana-Rodriguez F, Gerardo-Nieto O, et al. In?situ measurement of dissolved methane and carbon dioxide in freshwater ecosystems by off-axis integrated cavity output spectroscopy [J]. Environmental Science & Technology, 2014, 48(19): 11421-11428.

[13] [13] Wankel S D, Huang Y W, Gupta M, et al. Characterizing the distribution of methane sources and cycling in the deep sea via in?situ stable isotope analysis [J]. Environmental Science & Technology, 2013, 47(3): 1478-1486.

[14] [14] Michel A P M, Wankel S D, Kapit J, et al. In?situ carbon isotopic exploration of an active submarine volcano [J]. Deep Sea Research Part II: Topical Studies in Oceanography, 2018, 150: 57-66.

[15] [15] Demtroder W. Laser spectroscopy: Basic concepts and instrumentation, second enlarged edition [J]. Optical Engineering, 1996, 35(11): 3361-3362.