Field-Resolved Coherent Raman Spectroscopy of High Frequency Vibrational Resonances

Electric fields of coherent Raman signals are resolved with sensitivity for high-frequency vibrational resonances utilizing a four-pulse, trapezoidal beam geometry in a diffractive optic-based interferometer. Our experiments show that the heterodyne detected signal phase is stabilized for particular terms in the third-order response function by the cancellation of inter-pulse phases. The C-H stretching modes of cyclohexane and benzene are studied under two polarization conditions. The temporal profiles of signal fields for cyclohexane exhibit a low-frequency recurrence due to the interference between the signals associated with the symmetric and asymmetric C-H stretching modes. In contrast, the electronically nonresonant polarizability response of benzene gives rise to a significant broadband signal component in addition to that associated with its C-H vibrational resonance. Time-frequency shapes of the Raman signal fields are strongly dependent on the properties of the liquid and the polarizations of the laser pulses. Passively phase-stabilized heterodyned signal detection in transient grating and photon echo spectroscopies has recently been realized at optical frequencies by the incorporation of diffractive optics in four-wave mixing interferometers, thereby enhancing the sensitivity and information content of thes