Recent studies on signal enhancement of spontaneous Raman scattering for developing of sensitive Raman gas detectors are reported. Raman scattering is a gas detecting method with high feasibility, but usually its signal is very low. To improve the level and the quality of the Raman signal, the effects of pumping laser source, sample cell, and optical arrangement are studied in detail. It is found that not only the wall of sample cell will give a wide Raman or fluorescence background which will decrease the sensitivity, but the dichroic beam splitter will also contribute considerable background if it is not aligned properly. The sample cell of hollow fiber is characterized by its high responsibility as well as its high background and low signal contrast. When the hollow fiber is replaced by a free-space sample cell consisted of metal-coated parabolic reflector, the wide background is largely suppressed. If there is no common optical elements between the pumping and collecting optical systems, the wide background will be cut down obviously, which is proved by the intracavity-enhanced Raman scattering in a He-Ne laser. These experimental results will be helpful for the research and developing of highly sensitive Raman gas detectors.

Date Published: 31 May 2013
PDF: 8 pages
Proc. SPIE 8718, Advanced Environmental, Chemical, and Biological Sensing Technologies X, 87180N (31 May 2013); doi: 10.1117/12.2016345

Published in SPIE Proceedings Vol. 8718:
Advanced Environmental, Chemical, and Biological Sensing Technologies X
Tuan Vo-Dinh; Robert A. Lieberman; Günter G. Gauglitz, Editor(s)