Broadband Terahertz Polarimetry for Photonic and Biomedical Applications

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Proposal Title:Broadband Terahertz Polarimetry for Photonic and Biomedical AppllicationsInstitution: University of WashingtonThe proposed project will make significant contributions in imaging and sensing applications of various types of objects and materials and will contribute significantly to health monitoring, homeland security and medical applications. The broad scientific importance of terahertz technology is attested by the number of research programs and publications working to develop terahertz metrology techniques for a broad range of applications, including medical imaging, organic and polymer material science, and study of chiral molecules, amino acids and metamaterials. In particular, polarimetric methods will contribute to an understanding of physical interaction mechanisms and device physics in a range of applications. Our effort includes support for active dissemination of polarimetric capability to the broader research community. Moreover, this project is structured so as to enhance undergraduate and graduate research opportunities at the University of Washington, by providing training to student instrumentalists in terahertz polarimetric methods. Additionally, experimental results and research findings through this project will be disseminated in the form of guest lectures in a graduate-level course in Photonics. Finally, throughout this project, we will endeavor to identify and recruit female, disabled and under-represented minority students, at both undergraduate and graduate levels. Polarization measurement and ellipsometry are essential research techniques for investigating properties of new materials in many areas of basic sciences, which also find immediate industrial and biomedical applications. Broadband polarization measurement in the terahertz frequency regime presently suffers from several significant limitations: (1) Current terahertz polarimetry techniques offer only coarse polarization resolution and small isolation between orthogonal polarization channels, due in significant part to (2) poor ability to calibrate THz polarimeters, as a results of high frequency-dependent power loss in external polarizers; moreover (3) current terahertz polarimetry techniques require rotation of external polarizers to pre-determined fixed angles and positions, which burdens the system with lower measurement speed and inaccuracies in rotational polarizer placement.We propose development of a novel broadband terahertz polarimeter that combines two recent advancements in terahertz source and detector technology: A. Coherent control of complex polarizations of terahertz waves generated in gas plasmas, and B. Measurement of sample-induced ellipticity and cross-polarization using a novel full polarimetric broadband terahertz spectroscopy setup. Integrating these two techniques, we will demonstrate a polarization-agile terahertz polarimetry system capable of investigating cross-polarization and chirality of a wide variety of natural and manufactured targets. We will in particular demonstrate applications of the new polarimeter in two important applications, namely diagnosis of healthy and burned mammalian skin tissue and characterization of photonic devices based on graphene and nano-stuctured materials.