Precise phase shaping and characterization of the mid-infrared femtosecond pulses

Mid-infrared (MIR) pulses enable nonlinear vibrational spectroscopy and can unravel structural/vibrational dynamics of molecular systems. MIR pulses also provide a powerful way for coherent control of molecular dynamics at the electronic ground state. In order to control the vibrational transitions of different modes in a coherent manner, an accurate control of the amplitude and phase of a MIR pulse is necessary. In this report, the authors demonstrate a precise phase shaping of the MIR femtosecond pulse and its characterization. The spectral amplitude/phase modulation was achieved with a 4f-pulse shaper based on an acousto-optic modulator (AOM). An accurate evaluation of the shaped phase was achieved by exploiting the spectral interferometry technique.