Polaritonics Platform for Terahertz Signal Processing, MultipleScattering, and Field Enhancement

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Objective The objectives if this project are to investigate: (i) Multiply-scattered terahertz signals in sensing and imaging applications, and (ii) Terahertz field enhancement for spectroscopy. In Topic (i), models of multiple electromagnetic wave scattering will be tested using a terahertz polaritonics platform. Femtosecond laser machining will be used to drill holes and carve specified structures with different dimensions and spatial distribution properties into lithium niobate crystalline films. Terahertz waves will be generated and detected in the films. The results will guide the development of methods for terahertz imaging. In Topic (ii), doped semiconductor cavities and waveguides will be developed to provide terahertz field enhancement. The fields may be sufficient to drive highly nonlinear material responses including structural phase transitions and dielectric breakdown. This will permit direct time-resolved optical observation as well as extensive control over complex material transformations.Intellectual MeritThe terahertz spectrum has been underutilized, relative to microwaves and optics, in large part because of a dearth of sources and detectors. Recent progress in these areas presents opportunities for new methods for controlling terahertz signals, for imaging, and for spectroscopy, and these topics will be addressed. Broader ImpactTwo Ph.D. students will be supported by this award. At MIT, the project will dovetail with a planned expansion of a pre-college outreach program run by the Nelson group. At Purdue, undergraduate students will be recruited to work on this project in the Webb group.