Quantum-coherent molecular ensembles in plasma

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This award will support continued work based on the recent discovery that coherent rotational wavepackets in oxygen and nitrogen molecules in air can exert surprisingly strong control over high power femtosecond laser filamentation. The wavepackets manifest themselves in air as refractive index lenslets that propagate as quantum echo wakes following the filamenting laser pulse at its group velocity. A secondary pulse injected into these wakes, depending on the injection delay, can either be trapped and steered or scattered out of the beam axis. These results promise to allow much higher filament laser power, greatly extended filament lengths, increased electron density, and enhanced filament continuity, all essential for applications of femtosecond filaments, including terahertz generation, remote ionization, nonlinear light generation and atmospheric monitoring, and channels for electrical discharges. The proposed experiments represent a novel direction in plasma physics of some intellectual merit: the interaction of quantum coherent ensembles with plasmas. The award will also support another set of experiments in laser-nanoparticle interactions. The goal is to control the nanoplasma dynamics with the strong laser ponderomotive force, the high field analogue of inertial confinement.This highly interdisciplinary experimental and theoretical work provides an excellent training experience for graduate and undergraduate students. The physical ideas underlying the experiments, and the diagnostic techniques developed to measure ultrafast processes under extreme conditions, have a broad science and technology impact, from national defense to industry.