Raman effect Stokes wave

The first observation of the stimulated Raman effect was reported by Woodbury and Ng 215) j e effect was then thoroughly studied by several authors 216-218) and its theoretical background developed 219.220) (see also the review articles by Zubov et a/.22D). The stimulated Raman effect can be described as a parametric process where the coupling between a light wave at the Stokes frequency (Os and an optical phonon (vibrational wave) at cOy is produced by a pump field at col = (Oj + ojy. 

Other, related coherent Raman effects are also represented in Figure 5, such as the case (C) where the signal beam is detected at the Stokes frequency. The Raman-induced Kerr effect (B) may be interpreted as the quadratic influence of an electric field of frequency CO2 on the elastic scattering of radiation at a frequency or vice versa. In this case the phasematching (or wave-vector-matching) condition is fulfilled for any angle between beams 1 and 2, while in cases (A) and (C) it may only be met for certain angles of the beams with respect to each other. 

To determine the unconditional probability distribution for the spin-wave excitations Psw(n), we must find the effective number of transverse modes which contribute to the Raman processes. We identify two extreme regimes which permit analytic treatment a single mode regime where the number of excitations in the 87Rb cell follows Bose-Einstein (thermal) statistics and a multimode regime where it follows Poisson statistics. We find in both cases that the quantities F and Q depend on two experimental parameters 0 ( number of lost Stokes photons) and v ( noise to signal ratio), which are defined in Tab. 1. 

There are several classes of optical effects induced by an internal perturbation, such as saturation of absorption, coherent Raman spectroscopy, multi-photon absorption processes, coherent transient spectroscopy (see Table 0.3). Section 5.1 of this chapter deals with saturation of absorption and multi-photon absorption processes. Section 5.2 outlines the principles of coherent anti-Stokes Raman spectroscopy (CARS), Raman-induced Kerr effect spectroscopy (RIKES), four-wave mixing (FWM), and photon echo. 

Figure 5 Ladder graphs for four-wave mixing effects containing Raman processes. In all cases there is assumed an intermediate Raman-type resonance at the frequency Q. (A) The coherent anti-Stokes Raman (CARS) process. (B) The process responsible for stimulated Raman spectroscopy (SRS) as well as the Raman-induced Kerr effect (TRIKE). (C) The coherent Stokes Raman spectroscopy (CSRS). Adapted with permission from Levenson MD (1982), Introduction to Nonlinear Laser Spectroscopy. New York Academic Press.

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