Nonlinear Raman spectroscopies with Raman shifter for sensitive gas detection

Summary form only given. In recent years, measurements of the trace greenhouse gases such as CO/sub 2/, CH/sub 4/ has become important. In chemical plants and gas pipe lines, continuous monitoring of the leak of inflammable gases is also very important. We proposed a new scheme for nonlinear Raman spectroscopy, in which a fixed-frequency laser is combined with a Raman shifter. In this scheme, no IR tunable laser is required like absorption spectroscopy and photo-acoustic spectroscopy (PAS). We applied this scheme to different kinds of nonlinear Raman spectroscopy; photo-acoustic Raman spectroscopy (PARS), coherent anti-Stokes Raman spectroscopy (CARS) and stimulated Raman gain spectroscopy (SRGS).