Coherent anti-Stokes Raman spectroscopy (CARS): Improved experimental design and observation of new higher-order processes

Abstract

The development of the optical and electronic arrangement which has permitted the straightforward measurement of coherent anti‐Stokes Raman spectra (CARS) and of higher‐order processes not previously reported is described in this paper. The CARS spectrum of a dilute solution of diphenyloctatetraene in benzene is presented. This spectrum demonstrates the significantly greater signal‐to‐noise ratio possible with CARS as compared to conventional Raman techniques. Higher‐order Raman spectral excitation studies (HORSES) are described which indicate the presence of a six‐wave or a second‐order four‐wave mixing process.