Coherent spectroscopy and coherent control of collective modes through shaped optical fields

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In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Keith Nelson of MIT will develop and use new methods for optical control over molecules and materials. Electromagnetic pulses in the terahertz frequency range will be tailored to drive coherent rotational, vibrational, and electronic responses of polar molecules in order to understand structural and chemical dynamics in molecular gases, liquids, and solids. The terahertz fields will be accompanied by infrared and optical pulses to achieve coherent control over multiple responses that together can lead to structural and chemical change. The research is based on recently developed methods that have had broader impact as they have been taken up by basic and applied research groups around the world. The methods to be developed are likely to have similar impact and may enable novel applications in ultrafast light-driven switching and signal processing, generation of ultrahigh-frequency acoustic waves, and optical control over molecules and materials. Some aspects of the research are shared in a dedicated outreach lab in which high school students spend up to ten afternoons conducting experiments and analyzing their data, usually followed by presentations of their results in their school classes or science fairs. The students learn about modern optics and advanced materials as they fabricate thin-film samples and make optical measurements involving crossed laser beams that they align to generate and monitor surface acoustic waves that propagate in the films. The noncontact optical measurements are the same as those conducted in one of our labs and in a commercial instrument that is used in the microelectronics fabrication industry for metal film thickness determination.