Characteristics of picosecond coherent anti-stokes raman spectroscopy with mode-locked dye lasers in comparison with stimulated raman gain

Abstract

Time-resolved coherent anti-Stokes Raman scattering (CARS) has been performed with a double synchronously pumped mode-locked dye-laser system that is the same as had been used earlier for stimulated Raman gain (SRG) experiments; the CARS signal is also spectrally resolved. We present an extensive experimental and theoretical study of the CARS technique and compare the results with the characteristics of SRG. Experimental tests have been performed on the 656- and 991-cm−1 modes in liquid CS2 and C6H6, respectively. In particular, the influence of the pulse chirps on the time resolutions in CARS and SRG has been examined. SRG profits from oppositely chirped dye-layer pulses. In these circumstances, the observed time resolution in SRG is typically a factor of 3 better than in CARS. Also, when measured under off-resonance conditions, CARS decay curves exhibit a narrow and pronounced coherence spike that is symmetrical near zero delay: its appearance is discussed in detail. In addition, we establish the conditions for which the phenomena, of critical frequency mistuning and spectral narrowing in time-delayed CARS are observable. © 1990 Optical Society of America.