KSEF RDE: Photoconductive Antennas for Terahertz Spectroscopy and Imaging

Systems that rely on terahertz radiation are expanding rapidly. Terahertz applications include imaging systems based on backscatter and forward-scatter technology, material spectroscopy using pulsed radiation, and sensing of biomedical or other materials. Efficient and well-designed antennas in the terahertz range are necessary to achieve good performance in these areas, and photoconductive antennas are a promising candidate for use in these systems. Photoconductive antennas are voltage-biased, microstrip-type antennas fabricated on a photoconductive substrate that are excited by femto-second laser pulses. One advantage of photoconductive antennas is that they can be printed directly on a substrate using super-fine ink-jet printing technology. This effort will build on ongoing efforts by the University of Kentucky to develop state-of-the-art electromagnetic analysis software that is capable of analyzing complicated structures excited by broadband sources. The existing software toolkit is ideal for the design of photoconductive antennas and will be modified to model photoconductive antennas. Necessary modifications include creating accurate computational models for the antenna substrates, for the femto-second pulsed laser source, and for the bias-voltage. We then propose to study, design, and optimize various antenna configurations. In addition, the effect of layered substrates on antenna performance will be investigated. Optimized antennas will be fabricated and their characteristics compared to computation. Feasibility for the use of the antennas in material spectroscopy and spectroscopic imaging systems will be explored, and, in particular, experiments will be made concerning the measurement of complex dielectric constants of materials and image reconstruction of objects encased in an opaque material.