Search

We present a novel concept for the generation of ultrashort polarization-shaped bichromatic laser fields. The scheme utilizes a 4f polarization pulse shaper based on a liquid crystal spatial light modulator for independent amplitude and phase modulation of femtosecond laser pulses. By choice of either a conventional (p) or a composite (p-s) polarizer in the Fourier plane, the shaper setup enables the generation of parallel linearly and orthogonal linearly polarized bichromatic fields. Additional use of a γ/4 wave plate behind the setup yields co-rotating and counter-rotating circularly polarized bichromatic fields. The scheme allows to independently control the spectral amplitude, phase and polarization profile of the output fields, offering an enormous versatility of bichromatic waveforms. [ABSTRACT FROM AUTHOR]

Bichromatic polarization-shaped femtosecond laser pulses are used to control three-dimensional photoelectron momentum distributions (3D-EDs) from resonance enhanced multi-photon ionization of potassium atoms. The light fields consisting of two spectral bands with different ellipticity are produced using an ultrafast polarization pulse shaper equipped with a custom polarizer in the Fourier plane. The tomographically reconstructed 3D-EDs from ionization with counterrotating circularly or orthogonal linearly polarized bichromatic laser pulses show different angular momentum superposition states at four distinct photoelectron energies. The analysis of the measured 3D-EDs reveals that the underlying physical mechanism is based on the interplay of ionization pathway selection via quantum mechanical selection rules for optical transitions and intrapulse frequency mixing of the spectral bands with different ellipticity.