Enhancement of Raman modes by coherent control in β-carotene

The enhancement of vibrational modes by phase-shaped femtosecond laser pulses is studied under resonant and non-resonant conditions in an open loop coherent control experiment using non-linear Raman spectroscopy. Applying multipulse sequences matching the periodicity of single vibrations, the modes of β-carotene solvated in cylcohexane were not only specifically excited, but under resonant conditions also enhanced compared to the Fourier-limited case. This effect is attributed to an increased population transfer to the excited state and stronger coherences created and demonstrates the feasibility to selectively amplify ground state Raman modes by coherent control.