Coherent control of vibrational wave packet in condensed matters using amplitude- and phase-programmable pulses

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We developed all solid-state amplitude- and phase-programmable femtoseocnd optical source. Nearly transform-limited pulses from a Ti : sapphire seed laser is delivered into a programmable phase modulator. The phase modulator is composed of a pair of grating and spherical mirror, and liquid crystal spatial light modulator (LC-SLM). The temporal profile and phase information of the femtosecond pulses can be obtained from the FROG measurement. The measured phase information is processed in a PC and fed back to the SLM for adjustment of the phase mask. A desired phase pattern will be realized through the iterative adjustment.We measured excited-state population in a cyanine dye molecule using the phase programmable optical source. Wave packet motion on the excited-state was observed to be dependent on chirp direction and rate of excitation by femtosecond pulses. Strong reduction in excited state population is efficient for negatively chirped pulses in the cyanine dye molecule, which is explained in terms of a pump-dump process.We have performed a quantum mechanical calculation for an electronic two-level system coupled to a single vibrational mode, and successfully reproduced the experimental observation.