Raman anti-Stokes lasers

ABSTRACT. Tunable coherent radiation in the ultraviolet and vacuum ultraviolet has been generated by stimulated Raman scattering, by anti-Stokes Raman lasers, and by frequency mixing processes in nonlinear media. The theory and experimental progress in the development of these laser-driven sources is reviewed, and examples of available systems and their characteristics are discussed. Various applications in spectroscopy of radiation tunable in the wavelength region 200-90 nm are presented. 

Raman-laser emission in Se at 158.7 and 167.5 nm using pump-laser radiation at 199.5 and 254.8 nm, respectively. Anti-Stokes Raman lasers using Sn and Pb have also been reported [l6]. 

Figure 3. Experimental arrangement used to produce a Thallium anti-Stokes Raman laser [l3].

Figure 4. Energy levels involved in the Thallium anti-Stokes Raman laser with inverted population in the 6p 1 3/2 level and pump sources at 532 and 355 nm [l3].

In media with a population inversion between the ground state and an excited Raman-active level, radiation at the anti-Stokes wavelength can be produced through a process similar to the one just described for Stokes generation in media that start from the ground state. This combination, illustrated in Fig. 25, is termed an anti-Stokes Raman laser. It has been used to generate... 

FIGURE 25 Level diagram of anti-Stokes Raman laser in Tl. [Reprinted from White, J. C., and Henderson, D. (1982). Opt. Lett. 7, 517. Copyright 1982 by the Optical society of America.]... 

B. Wellegehausen, K. Ludewigt, H. Welling Anti-Stokes Raman lasers. SPIE Proc. 492, 10 (1985)... 

New metliods appear regularly. The principal challenges to the ingenuity of the spectroscopist are availability of appropriate radiation sources, absorption or distortion of the radiation by the windows and other components of the high-pressure cells, and small samples. Lasers and synchrotron radiation sources are especially valuable, and use of beryllium gaskets for diamond-anvil cells will open new applications. Impulse-stimulated Brillouin [75], coherent anti-Stokes Raman [76, 77], picosecond kinetics of shocked materials [78], visible circular and x-ray magnetic circular dicliroism [79, 80] and x-ray emission [72] are but a few recent spectroscopic developments in static and dynamic high-pressure research. 

Figure B2.3.8. Energy-level sehemes deseribing various optieal methods for state-seleetively deteeting ehemieal reaetion produets left-hand side, laser-indueed fluoreseenee (LIF) eentre, resonanee-enlianeed multiphoton ionization (REMPI) and right-hand side, eoherent anti-Stokes Raman speetroseopy (CARS). The ionization oontinuiim is denoted by a shaded area. The dashed lines indieate virtual eleetronie states. Straight arrows indieate eoherent radiation, while a wavy arrow denotes spontaneous emission.

Major breakthroughs in early ultrafast VER measurements were made in 1972 by Laubereau et al [22], who used picosecond lasers in an SRS pump-incoherent anti-Stokes Raman probe configuration, to study VER of C-H... 

An interesting variation of Raman spectroscopy is coherent anti-Stokes Raman spectroscopy (CARS) (99). If two laser beams, with angular frequencies CO and CO2 are combined in a material, and if cjj — is close to a Raman active frequency of the material, then radiation at a new frequency CJ3 = 2cJ2 — may be produced. Detection of this radiation can be used to characterize the material. Often one input frequency is fixed and the other frequency, from a tunable laser, varied until matches the Raman frequency. CARS has the capabiHty for measurements in flames, plasmas, and... 

Farrow R. L., Rahn L. A. Interpreting coherent anti-Stokes Raman spectra measured with multimode Nd YAG pump lasers, J. Opt. Soc. Am. B2, 903-7 (1985). 

The present study demonstrates that the analytic calculation of hyperpolarizability dispersion coefficients provides an efficient alternative to the pointwise calculation of dispersion curves. The dispersion coefficients provide additional insight into non-linear optical properties and are transferable between the various optical processes, also to processes not investigated here as for example the ac-Kerr effect or coherent anti-Stokes Raman scattering (CARS), which depend on two independent laser frequencies and would be expensive to study with calculations ex-plictly frequency-dependent calculations. 

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 ... 

Early picosecond studies were carried out by Schneider et al, [63] on the parent spiro-oxazine (NOSH in Scheme 8) and similar derivatives. In a back-to-back work, they also described a complimentary CARS (coherent anti-Stokes Raman spectroscopy) investigation [69], Simply put, these authors found that the closed spiro-oxazine ring opened in 2-12 psec after laser excitation. The reaction was slower in more viscous solvents. An intermediate state formed within the excitation pulse and preceded the formation of merocyanine forms. This transient was named X in deference to the X transient named by Heiligman-Rim et al. for the spiropyran primary photoproduct [8], (See also the previous section.) The name X has since been adopted by other workers for the spiro-oxazines [26,65],... 

Broadband Laser Source and Sensitive Detection Solutions for Coherent Anti-Stokes Raman Scattering Microscopy... 

Kee, T. W., and Cicerone, M. T. 2004. Simple approach to one-laser, hroadhand coherent anti-Stokes Raman scattering microscopy. Opt. Lett. 29 2101-03. 

Potma, E. O., Jones, D. J., Cheng, J.-X., Xie, X. S., and Ye, J. 2002. High-sensitivity coherent anti-Stokes Raman scattering microscopy with two tightly synchronized picosecond lasers. Opt. Lett. 27 1168-70. 

Greve, M., Bodermann, B., Telle, H. R., Baum, P, and Riedle, E. 2005. High-contrast chemical imaging with gated heterodyne coherent anti-Stokes Raman scattering microscopy. AppZ. Phys. B-Lasers Opt. 81(7) 875-79. 

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