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 Title: IMPLICATIONS OF SELF-PHASE MODULATION (SPM) FOR N2 FEMTOSECOND COHERENT ANTI-STOKES RAMAN SCATTERING (FS CARS) SPECTROSCOPY AT ELEVATED PRESSURE Author(s): Gu, Mingming Contributor(s): Lucht, Robert P. ; Satija, Aman Subject(s): Spectroscopy as an analytical tool Abstract: \begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.8]{4species.eps} \end{wrapfigure} Femtosecond coherent anti-Stokes Raman scattering (fs-CARS) is a non-linear spectroscopic technique that has been widely used in various combustion related environments to measure the temperature and species concentration information. On the other hand, self-phase modulation (SPM) describes a Kerr-like effect in which an ultrashort pulse accumulates nonlinear phase as it propagates through the gas medium like N$_{2}$. As a result, the application of fs-CARS in the high pressure environment will inevitably need to deal with SPM influence especially when at high laser intensities. We evaluated the SPM effects by measuring the optical spectra of the ultrashort pulses as well as the fs-CARS spectrum transmitted through our custom-designed high-pressure vessel. Different SPM patterns and the extent of SPM were evaluated for gaseous species like N$_{2}$, CO$_{2}$ and CH$_{4}$. With the suppression of SPM by reducing the laser intensity, fs-CARS spectrum in pure N$_{2}$ was successfully fitted for pressure range from 1 to 10 bar. This study is meaningful not only for the study of fs-CARS measurement but also for all the other ultrafast spectroscopic studies at high pressure conditions, especially when the laser beams need to be focused or if the optical path inside the high pressure chamber is significant. Issue Date: 2019-06-20 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104370 DOI: 10.15278/isms.2019.RL05 Rights Information: Copyright 2019 Mingming Gu Date Available in IDEALS: 2019-07-152020-01-25
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