Terahertz (THz) imaging is emerging as a promising new technology, and exploration of this potential by the scientific community has finally become possible with advances in ultrafast optical lasers to generate THz pulses. The goal of this research program is to characterize broadband Terahertz (THz) pulse propagation and scattering in random media with the development of advanced electromagnetic (EM) models that are integrated into a rigorous systems simulation framework. These models will additionally be utilized as an interactive learning tool for electromagnetics education and to provide an avenue for integration of undergraduates into the research process. Successful completion of the research e_ort will result in significant advances in understanding of THz propagation characteristics, with specific focus on application of THz spectroscopy to detection of explosives and to medical imaging. The computational models will also facilitate the development of computer-based visualization tools that will incorporate research into lecture and laboratory environments. The process will be documented with comprehensive guidelines and evaluated quantitatively in terms of the impact on student learning and development. These will be disseminated to the wider educational community by posting to the internet and presentation in educational journals such as the American Society for Engineering Education.
The proposed research consists of the development of computational software for the prediction of THz field statistics from random media, and the incorporation of this calculation into a system characterization which includes the quantum mechanical (QM) framework and the spectrum of the THz pulse generation. The activity thus requires: 1) development of particle-based and continuously varying random medium models to represent the inhomogeneities of the explosive and biomedical materials, 2) extension of EM scattering theory to account for particle resonances and dispersion that occur at THz wavelengths, 3) application of Fourier synthesis to combine the QM, EM, and system spectral components to generate the time domain response, 4) validation of the resulting models through a collaborative experimental activity with the University of Washingtons (UW) THz measurement facility, and 5) incorporation of the models into educational activities.
Intellectual Merit. The proposed activity has substantial intellectual merit. It will significantly advance understanding of THz wave propagation, while simultaneously providing a rigorous assessment of random media models and techniques for EM scattering calculation. The code will be developed in the PIs well-equipped Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab) at Portland State University (PSU), and will leverage previous research activities in which the PI developed random medium models and scattering formulations for microwave propagation through densely packed systems of spheres. A unique component of the proposed approach is the process for synthesizing the time domain response to obtain a rigorously derived end-to-end integrated system response that captures the complicated scattering physics and provides the ability to explore and assess the potential application of THz imaging for a variety of materials.
Broader Impacts. The proposed activity will advance scientific understanding while simultaneously enriching the educational environment through development of visualization tools and an accompanying procedure for the incorporation (and evaluation) of undergraduate students into the research process. It will promote partnership between PSU and UW through shared use of experimental facilities, and strengthen the participation of women in each of these institutions by providing a role model for women in engineering through the leadership of the (woman) PI. The potential societal benefits are truly impressive, including the ability to detect harmful explosive devices or detect the presence of cancer. The scientific results will be broadly disseminated through scientific journals and technical conferences.
