1 Liquid-Core Waveguide for Enhanced Laser Raman Spectroscopy in Oceanic Applications

• Main Authors: Jonathan Scholl, Mentors Peter Brewer, Edward Peltzer, Peter Walz
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Raman Spectroscopy; Waveguide; Bicarbonate; DORISS; Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.598.451; http://www.mbari.org/education/internship/06interns/papers/JScholl.pdf

Over the past five years, the Brewer Lab Group at MBARI has effectively used DORISS (Deep Ocean Raman In Situ Spectrometer) for oceanic chemistry studies. Laser power limitations have thus far constrained the sensitivity of the system, preventing the observation of the natural trace concentrations of bicarbonate in seawater (2 mmol/kg), a crucial indicator of the CO2/Carbonic Acid/Bicarbonate/Carbonate balance in the ocean. Liquid-core waveguides have been previously shown to amplify the Raman scattering signal returning to the detector by up to two orders of magnitude by increasing the laser light path length through the sample. In this study, we have created an effective waveguide setup for a laboratory-based Raman spectrometer, witnessing amplification gains of nearly an order of magnitude on seawater samples and aqueous bicarbonate solutions.