A phase-sensitive detection method that uses two diffractive optics for femtosecond nonresonant Raman spectroscopy is demonstrated. One diffractive optic is used for generating the three input pulses for the third-order nonlinear experiment, and the second is used for recombining the signal with a passively phase-locked local oscillator derived from the probe pulse. This approach allows for phase-sensitive detection, direct phase calibration, control over all field polarizations, and removal of unwanted two-pulse signal contributions. Experiments on the intermolecular dynamics of CS2 and CH3CN demonstrate that the birefringent (in-quadrature) signal amplitude is significantly greater than the dichroic tin-phase) contribution. Polarization selective measurements are used to project the isotropic birefringent response for CS2, which suppresses reorientational dynamics and allows interaction-induced effects to be observed.