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Coherent anti-Stokes Raman scattering (CARS) spectroscopy is applied to diagnostics of phase behavior of a fluid in pores of nanoporous glasses. Samples with mean pore radii of 2 and 3.5 nm were filled with compressed carbon dioxide at near-room temperatures. CARS spectra of the 1388 cm −1 Q-branch were measured at isothermal compressing in a wide pressure range including the transition from gaseous to condensed state. The spectra show specific transformations caused by fluid adsorption and condensation in nanopores. We have carried out calculations of the spectral profiles based on the phase behavior of carbon dioxide in cylindrical glass nanopores. Phase behavior modeling was performed using thermodynamic concepts of surface adsorption and capillary condensation. A good agreement between experimental spectra and calculations was obtained. The potential of CARS technique for the diagnostics of fluid phase behavior in pores and for the characterization of nanoporous host structure is discussed.

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Coherent anti‐Stokes Raman scattering (CARS) spectroscopy is applied to probe the microstructure of CO2 adsorbed in nanoporous glass Vycor with a mean pore radius of 2 nm. CARS spectra of the Q‐branch (1388 cm‐1) were measured at 22 °C at pressures decreasing in a range providing the transition from the condensed phase in the whole volume of the pores to submonolayer coverage on their walls. The spectral behavior demonstrates sequential changes in the fluid state inside the nanopores. The analysis of the experimental results allowed us to characterize and compare the spectral properties of gas‐like, liquid‐like, and surface adsorbed carbon dioxide. The results provide clear evidence that as the surface coverage is decreased, the vibrational frequency shifts down. Copyright © 2014 John Wiley & Sons, Ltd.

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Coherent anti-Stokes Raman scattering (CARS) spectroscopy is applied to investigate the fluid phase behavior in small mesopores at bulk sub-and supercritical temperatures. CARS spectra of the Q-branch (1388 cm À1 ) of carbon dioxide were measured at isothermal compression in pores of two nanoporous glass samples with pore radii of 2 and 3.5 nm. The spectral transformations with pressure of the fluid indicate the formation of a condensed phase in the volume of pores that clearly demonstrates the shift of the critical point. The spectrum of carbon dioxide condensed in the wider pores corresponds approximately to the critical density in bulk. In the narrower pores, the spectrum is noticeably shifted towards the lower wavenumbers that correspond to higher density of condensed fluid.

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The nature of cubic and cascaded quadratic nonlinear responses in the KTiOPO4 crystal under picosecond pump is studied. The main attention is paid to determination of the origin and properties of the blue radiation accompanying the red light amplification process (the central wavelength ~685 nm, bandwidth ~20 nm) in a noncollinear optical parametric amplifier (NOPA) pumped by the second‐harmonic radiation of the picosecond Nd:YAG laser (532 nm). In NOPA, the amplified seed radiation (ωs) becomes so intense that it can participate in any nonlinear three‐wave interaction and also can play the role of the Stokes wave in the in the coherent anti‐Stokes Raman scattering‐process in which powerful pump radiation (ωp) of the main parametric process serves both as the pump wave and the probe wave. Possible causes of the blue light emanating from the KTP crystal and the mechanisms for their realization are analyzed. We interpret the ring of blue light around the axis located between the directions of propagation of the green pump beam and the red beam of the amplified seed radiation, as the emission of amplified parametric fluorescence (signal wave) under low‐frequency pump. This phenomenon can be used for effective amplification in picosecond NOPA of weak anti‐Stokes radiation in the experiments with time‐resolved broadband picosecond coherent Anti‐Stokes Raman Scattering.