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

在这个由化学部化学结构、动力学和机制计划支持的项目中，麻省理工学院的基思纳尔逊将开发和使用对分子和材料进行光学控制的新方法。太赫兹频率范围内的电磁脉冲将被定制为驱动极性分子的相干旋转，振动和电子响应，以了解分子气体，液体和固体中的结构和化学动力学。太赫兹场将伴随着红外和光脉冲，以实现对多种反应的相干控制，这些反应共同导致结构和化学变化。该研究基于最近开发的方法，这些方法具有更广泛的影响，因为它们已被世界各地的基础和应用研究小组采用。待开发的方法可能会产生类似的影响，并可能在超快光驱动开关和信号处理，超高频声波的产生以及分子和材料的光学控制方面实现新的应用。研究的某些方面在一个专门的外展实验室中共享，高中生在其中花费长达十个下午的时间进行实验和分析数据，然后通常在学校课堂或科学展览会上展示他们的结果。学生们学习现代光学和先进材料，因为他们制造薄膜样品，并进行光学测量，涉及交叉激光束，他们对齐，以产生和监测表面声波在薄膜中传播。非接触式光学测量与在我们的实验室之一和在微电子制造行业中用于金属膜厚度测定的商业仪器中进行的测量相同。

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.