A non-dispersive approach for a Raman gas sensor

Abstract

Although Raman spectroscopy is widely used on solids and liquids, its application on gaseous samples is far less commonplace due to technical issues related to dealing with very weak signals over a strong background. A demonstration of a possible approach for a simple, noninvasive Raman-based gas detector is presented and evaluated. This setup is meant to perform nitrogen and oxygen gas concentration measurements through Raman scattering working with optical filters instead of the traditional spectrograph and a lighting-grade 532 nm diode-pumped solid state laser as the pumping source. An industrial-grade CMOS camera is used as the detector, taking full advantage of the low noise and spatial resolution of this device. The system has been tested for both oxygen and nitrogen in a gas flow cell. Nitrogen measurement in a glass vial is reported in order to demonstrate and show some of the advantages that could be obtained with the use of an imaging detector instead of a single pixel one. The reported measurements show that even without using a dispersion spectrometer, this approach enables an indicative, noninvasive gas detection through glass vials with significant rejection of the elastic scattering contribution.