Probing Far-Infrared Excitations of Surfaces and Thin Films by Optoelectronic Techniques

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In this project, part of the Cross-Directorate program for Multidisciplinary Research in Optical Science and Engineering, Tony Heinz at Columbia University together with colleagues from several other industrial and government laboratories will use optoelectronic techniques to probe in the far-infrared spectral region excitations of molecules and phonons in surfaces and thin films. These researchers will develop and refine coherent far infrared spectroscopy to study surface and interface problems and will apply this technique to a wide range of hitherto intractable measurements of surfaces and thin films. Multiple reflection and new waveguide geometries will enhance the sensitivity of the technique for surfaces and thin films, and sum-frequency generation schemes will mix broadband far infrared radiation with a spectrally narrow visible wavelength laser pulse. Ultrafast time-resolved measurements will also be exploited in several studies. Materials systems to be examined include ionic dopants in polymeric thin films, thin ferroelectric films, and marginal metals. Surfaces and thin films involve a limited quantity of material, and methods sensitive enough to study these systems are usually inadequate. This research program will lead to new techniques for measuring very low energy excitations at the surfaces of such condensed matter systems using novel optoelectronic methods. A broad cross section of materials and problems will be examined which have significant technological relevance and importance.