Stimulated Raman gain

Kroon R., Baggen M., Lagendijk A. Vibrational dephasing in liquid nitrogen at high densities studied with time-resolved stimulated Raman gain spectroscopy, J. Chem. Phys. 91, 74-8 (1989). 

Figure 3.6-4 Schematic diagram for a few techniques in nonlinear (coherent) Raman spectroscopy (CSRS Coherent Stokes Raman Spectroscopy SRGS Stimulated Raman Gain Spectroscopy IRS Inverse Raman Spectroscopy (= SRLS Stimulated Raman Loss Spectroscopy) CARS Coherent anti-Stokes Raman Spectroscopy PARS Photoacoustic Raman Spectroscopy).

Stimulated Raman gain and inverse Raman spectroscopy (SRGS, IRS)... 

The methods of nonlinear Raman spectroscopy, i. e. spontaneous hyper Raman scattering (based on the hyperpolarizability) and coherent nonlinear Raman scattering (based on the third-order-nonlinear susceptibilities) are discussed in detail in Sec. 3.6.1. In Sec. 3.6.2 the instrumentation needed for these types of nonlinear spectroscopy is described. In this section we present some selected, typical examples of hyper Raman scattering (Sec. 6.1.4.1), coherent anti-Stokes Raman. scattering (Sec. 6.1.4.2), stimulated Raman gain and inverse Raman spectroscopy (Sec. 6.1.4.3), photoacoustic Raman spectroscopy (Sec. 6.1.4.4) and ionization detected stimulated Raman spectroscopy (Sec. 6.1.4.5). 

The advantages of the two coherent Raman techniques, stimulated Raman gain (SRGS) and inverse Raman spectroscopy (IRS), have been described in detail in Secs. 3.6.1.3 and 3.6.2.3. Here, we present an instructive example for each technique emphasizing the high resolution capability of the.se methods. 

Figure 6.1-25 High resolution multi-pass stimulated Raman gain spectrum (SRGS) of the Q-branch of the lower component of the Fermi resonance diad of C 02 at a pres.sure of 200 Pa (1.5 Torr) (Saint-Loup et al., 1990).

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. 

Inverse Raman scattering Inverse Raman scattering (IRS) is a coherent process involving stimulated loss at an anti-Stokes-shifted frequency. The term inverse Raman refers to the fact that, at resonance, the probe radiation is attenuated. In spontaneous Raman spectroscopy, on the other hand radiation at Raman-active frequencies would he generated in the course of the experiment. Inverse Raman scattering (IRS) and stimulated Raman gain (SRG) are closely related. While one involves stimulated gain at an anti-Stokes-shifted frequency, the other involves stimulated loss at a Stokes-shifted frequency. 

Nonlinear Raman spectroscopy The nonlinear techniques include stimulated Raman scattering (SRS), hyper Raman, stimulated Raman gain (SRG), inverse... 

Michele Marrocco, PhD, is a researcher in laser spectroscopy at ENEA (Rome, Italy) (1999 to present). He received his degree in physics from the University of Rome in 1994. He was employed as a postdoctorate at the Max-Planck Institute for Quantum Optics (Munich, Germany), as a researcher at the Quantum Optics Labs at the University of Rome (Rome, Italy), and as an optics researcher by the army. His research activities include traditional and innovative spectroscopic techniques for diagnosis of combustion and nanoscopic systems studied by means of optical microscopy. The techniques used include adsorption, laser induced fluorescence, spontaneous Raman, stimulated Raman gain, stimulated Raman loss, coherent anti-Stokes Raman, degenerate four wave mixing, polarization spectroscopy, laser induced breakdown, laser induced incandescence, laser induced thermal gratings. He has over 30 technical publications. 

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