  We introduce the first method to enable an optical amplification of a
coherent Raman spectroscopy signal called radio frequency Doppler Raman
spectroscopy. Doppler Raman measurements amplify the optical signals in
coherent Raman spectroscopy by converting a spectral frequency shift imparted
by an impulsive coherent Raman excitation to a change in a probe pulse transit
time. This transit time perturbation is detected through the phase of a radio
frequency electronic signal measured at a harmonic of the probe pulse train. By
exploiting this new capability to scale the signal of a coherent Raman
spectroscopic signal, we open the potential to detect very weak Raman
spectroscopy signals that are currently not observable due to limits of
illumination intensity imposed by laser damage to the specimen.
