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Cold seep and hydrothermal vent system have unique function in mass circulation of the earth, and have been explored by in situ detection technologies in past decades. A brief review on the development and the newest applications of in situ laser spectroscopy for deep sea research is presented here. The laser Raman spectroscopy and laser induced breakdown spectroscopy, with the advantages exactly meeting the requirement of the in situ detection, are emphatically introduced in this paper. The prospect of the in situ laser spectroscopy for the possible application in the deep sea is also discussed in this paper, aiming to provide a reference for the future development of spectroscopy.

Characteristics of the secondary breakdown of dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in bulk water were investigated with different axial focusing arrangements and laser energies of the second laser pulse. Compared to the pre-focus or in-focus arrangement, post-focus arrangement could provide both stronger emissions and better repeatability within the energy range of 20–40 mJ. Such phenomenon is directly related to the breakdown characteristics in different conditions. Especially for in-focus arrangement, i.e. the most reported case of DP-LIBS in bulk water, the breakdown all occurs at the bubble boundary rather than inside the gaseous bubble even using a quite large laser energy of 130 mJ. The simulation results further confirm the secondary breakdown could not occur directly in gas of the bubble interior under the present experimental setup.