Coherent anti-Stokes Raman spectroscopy (CARS) is becoming the technique of choice for femtosecond time-resolved studies, say researchers at Weizmann Institute of Science in Rehovot, Israel, but its selectivity suffers because of the large bandwidth of its pulses. Now the researchers have used quantum coherent control to extract 15-cm^-1resonant signals from a probe pulse with a 120-cm^-1 bandwidth.

Reporting in the Feb. 11 issue of Physical Review Letters, the team describes how it employed a liquid crystal spatial light modulator to perform Fourier transform pulse shaping on the 810-nm output from a mode-locked Ti:sapphire laser that served as the probe. Broadening the excitation and probe pulses, the group suggests, should enable even higher-resolution spectral data.