Abstract

Coherent Raman beats have been suggested as a spectroscopic technique for studying energy-level splittings between sublevels of electronic ground states as well as electronically excited states. The process can be understood as a coherent Raman scattering experiment, as shown schematically in Fig. 1. It consists of an excitation step, in which a pump laser pulse creates a coherent excitation in the medium, represented by the wavy line connecting the two lower states. The presence of this coherence in the medium changes the nature of the Raman scattering process for the detection step qualitatively: in coherent Raman scattering, the amplitude of the Raman field is linear in the incident field.² The scattering process can thus be observed at low optical power, using cw lasers. The coherent Raman beat signal, which is observed in such an experiment, can be Fourier-trans formed to obtain a sublevel spectrum.

© 1994 IEEE