2020 年 62 巻 199 号 p. 40-48
This paper describes fundamentals of coherent anti-Stokes Raman spectroscopy/scattering (CARS). A brief review of the theoretical background of CARS as one of the third-order nonlinear optical processes. The third-order nonlinear optical susceptibility and the calculation of theoretical spectrum are explained including pressure narrowing phenomenon. The effects of the slit function, the spectral line shape of pump and Stokes lasers are discussed, and the examples of the observed CARS spectra are shown. Temperature measurement and improvement of accuracy are explained. The experimental results of unburned gas temperature in a spark ignition engine are shown as an example of the high accuracy CARS thermometry. The chirped-probe-pulse femtosecond CARS thermometry is introduced as a latest research activity.