Abstract：Great chemical and thermal gradient exists in deep sea hydrothermal vent environments, and rapid and turbulent mixing and biologic processes produce a multitude of diverse mineral phases and foster the growth of a variety of chemosynthetic micro-organisms. Raman spectrometer system is well suited to mineral speciation measurements and has been successfully used for deep sea hydrothermal environments detection so far. However, to further understand the interaction between mineral and microbial processes, a Raman system optimized for mineral identification that incorporates a fluorescence for microbial processes is necessary. In this paper, a combined Raman-fluorescence spectroscopy prototype was presented and some preliminary results were obtained. In this prototype, a double wavelength laser was used as the same excitation source for both Raman spectroscopy and fluorescence which worked at 532 and 266 nm, respectively. The laser was splitted into two paths based on wavelength and illuminated on the sample. The produced Raman and fluorescence signals were collected by a back-scattering optical set-up and coupled into a QE65000 and an USB2000 optical fiber spectrometer, respectively. With this prototype, we measured seawater and pseudo-nitzschia samples and got Raman and fluorescence spectra simultaneously for both samples, including sulfate Raman and CDOM fluorescence spectra in seawater sample, carotenoid Raman, proteoid and chlorophyll fluorescence spectra in pseudo-nitzschia sample. The results proved the feasibility of developing a compact Raman-fluorescence combined system for underwater detection.
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