Optofluidic jet waveguide enhanced Raman spectroscopy

An optofluidic device based on a liquid jet waveguide has been successfully applied in Raman spectroscopy. The sample under analysis is used to produce a liquid stream by means of a capillary nozzle. The waveguiding nature of the stream is used to effectively collect the Raman signal arising from chemical compounds when opportunely excited. An aligned configuration allows a direct coupling between the liquid jet and a multimode optical fiber used to deliver Raman signal toward the detection system. This approach avoids any necessity to contain the solution by solid walls and removes any background signal coming from the substrate that commonly affects Raman measurements. Two different set-up configurations are proposed and compared in terms of excitation/collection efficiency. Experimental measurements performed on ethanol-water solutions show high sensitivity enhancement of our sensor with respect bulk measurements. Measurements performed on potassium nitrate solution show high potentiality of our optofluidic sensor in water quality analysis and monitoring.