Differential femtosecond coherent Stokes and anti-Stokes Raman   spectroscopy
  We demonstrate a novel technique of coherent Raman spectroscopy with a femtosecond laser. We apply to a molecular sample a sequence of pairs of ultrashort excitation and probe pulses, with a linearly increasing time delay between the two pulses from one pair to the next. We measure, as a function of the delay, the intensity modulation in the signal resulting from the differential detection of the Stokes and anti-Stokes radiations generated at the sample. The Fourier transform of such time-domain signal reveals the spectrum of the excited vibrational Raman transitions. The experimental proof-of-principle demonstrates high resolution, broad spectral span and suppression of the non-resonant background, as well as sensitivity enhancement due to the differential detection. 
Takuro Ideguchi, Simon Holzner, Ming Yan, Guy Guelachvili, Theodor W.   H\"ansch and Nathalie Picqu\'e
physics.optics physics.chem-ph