Coherent Stokes Raman scattering, CSRS

More useful in spectroscopic terms is the process of coherent Stokes Raman scattering (CSRS) or anti-Stokes Raman scattering (CARS). This involves radiation from two laser sources of photon energy hvi>hv2 that irradiate the sample simultaneously. 

In order to extend the range of 2laser excitation, both CARS (Coherent Anti-Stokes Raman Scattering) and CSRS (Coherent Stokes Raman Scattering) are used. In both cases <03 = 2003 -U2 In the CARS mode 0)3 > wj > (03 in the CSRS mode <02 > (1)3. One-photon resonance effects are the same in both cases as described later. Phase matching is also the same in both cases with 3 = 2 ... 

Raman scattering (IRS), coherent anti-Stokes Raman spectroscopy (CARS), and coherent Stokes Raman spectroscopy (CSRS). Figure 3 shows Quanmm diagrams of the nonlinear Raman processes, with spontaneous Raman included as... 

The anti-Stokes/Stokes electric field produced by the CARS/CSRS (Coherent Stokes Raman Scattering) process at the focus is given by ... 

In addition to CARS, other closely related but less commonly used nonlinear Raman techniques have been developed. The energy level diagram for coherent Stokes Raman spectroscopy (CSRS) is shown in Figure 1. Unlike CARS, CSRS is nonparametric the final state is not the same as the initial state. Therefore, CSRS spectra may exhibit extra peaks due to coherence dephasing. Furthermore, the CSRS output beam is generated to the Stokes (lower frequency) side of 0)3. CSRS is therefore more susceptible to spectral interference from fluorescence and Rayleigh scattering of the input beams. 

Coherent Raman spectroscopy Coherent Raman spectroscopy is a term that refers to a series of closely related nonlinear Raman techniques in which the scattered Raman radiation emerges from the sample as a coherent beam -coherent meaning that the photons are all in phase with one another. The coherent techniques include Stimulated Raman Scattering (SRS), Coherent anti-Stokes Raman Spectroscopy (CARS), Coharent Stokes Raman Spectroscopy (CSRS), and Stimulated Raman Gain Spectroscopy (SRGS). Although most of the nonlinear Raman techniques are also coherent techniques, there is one incoherent nonlinear Raman process called Hyper Raman. 

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