Bulletin of the American Physical Society
2008 Joint Meeting of the APS Ohio-Region Section, the AAPT Southern Ohio Section, and the ACS Dayton-Section
Volume 53, Number 8
Friday–Saturday, October 10–11, 2008; Dayton, Ohio
Session C1: Terahertz Spectroscopy |
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Chair: Doug Petkie, Wright State University Room: Fawcett Hall 204 |
Saturday, October 11, 2008 8:00AM - 8:12AM |
C1.00001: Nondestructive Evaluation of Aerospace Composites Jeremy Johnson, Christopher Stoik, Matthew Bohn, James Blackshire Recent experiments will be presented demonstrating the utility of terahertz radiation for the nondestructive evaluation of delaminated, burned, and damaged fiber glass aerospace composites. Terahertz images of these prepared composites are presented using both the phase and amplitude of the terahertz radiation. The experimental setup has been demonstrated using both a reflective and transmissive terahertz geometry. A comparison of terahertz radiation for NDE will be made versus conventional NDE techniques such as x-ray tomography, ultrasound, eddy currents and optical coherence tomography. The specific application of this technique for NDE of aerospace composites will be discussed. [Preview Abstract] |
Saturday, October 11, 2008 8:12AM - 8:24AM |
C1.00002: Combustion Diagnostics with Terahertz Tomography Nicholas Schroeder, Fin Eichorn, Jason Deibel The objective of this project is to capture the spectroscopic signature and temperature of combustion process as a function of position using terahertz (THz) time-domain spectroscopy and imaging. The development of a system that can monitor the temperature of an exhaust plume and its chemical make-up as a function of position would be of immeasurable value to the further development of jet engines and their mid-life diagnostics. Current techniques available require different set-ups for each measurement, position and chemical. Our approach to tomographic reconstruction consists of utilizing 8 separate THz transmitter- receiver pairs arranged around the object, allowing all of the tomographic slices to be taken at the same instant. We will present preliminary data demonstrating THz tomographic imaging of solid objects and calibration of spectroscopic and thermal measurement capabilities by THz characterization of water vapors and flames. We will further show ongoing work to produce a THz tomographic reconstruction of a simple flame. [Preview Abstract] |
Saturday, October 11, 2008 8:24AM - 8:36AM |
C1.00003: Predicting the generation of THz fields based on measurements of amplitude and phase of the input field Peter Powers, Wenzao Li, Joseph Haus, Qiwen Zhan A common technique for terahertz (THz) generation is the optical rectification of an ultrashort laser pulse in ZnTe. The resultant THz field is dependent on the input field properties as well as the dispersion and loss in the optical rectification crystal. After the THz field is generated it propagates through the atmosphere for a set distance after which it can be measured using a gated electro-optic measurement. With a complete knowledge of the input pulse, the material dispersion and loss properties, and the transmission properties through the atmosphere, it is possible to model the measured THz field. We will present a model that predicts the THz field based on direct measurement of the input field using frequency resolved optical gating (FROG), the dispersion and loss properties of ZnTe, and the transmission properties of the atmosphere. The pulse shape of the ultrashort pulse can be modified using a grating compressor to frequency chirp the input field. We will compare the results of the model with the experimentally measured THz field for several different pulse shapes. [Preview Abstract] |
Saturday, October 11, 2008 8:36AM - 8:48AM |
C1.00004: Terahertz spectroscopy of gas phase molecules for chemical physics applications Douglas T. Petkie By far the most successful chemical physics application in the terahertz region has been high resolution spectroscopy of gas phase molecules. Laboratory investigations probe the molecular structure and intramolecular forces of a molecule and make possible the expansive databases for monitoring chemical species in the upper atmosphere and identification of molecules in the interstellar medium. Translating these technologies to terrestrial applications can be challenging due to broad line widths at atmospheric pressures. An overview of laboratory and remote sensing applications will be presented as well as the challenges of terrestrial remote sensing. [Preview Abstract] |
Saturday, October 11, 2008 8:48AM - 9:00AM |
C1.00005: Nondestructive materials characterization using sub-millimeter wave imaging Izaak Kemp, Douglas T. Petkie A sub-millimeter continuous wave system can be used to image corrosion pitting and structural defects in common aircraft materials such as aluminum 2024. In order to avoid failure of components during operation, many aircraft parts are replaced earlier than necessary leading to higher costs that could be reduced if the degree of damage in the component material could be determined non-destructively. Sub-millimeter wave systems are ideally suited for this purpose because of their ability to penetrate through substances such as paint, oil, and epoxy commonly found on the surfaces of aircraft. We will discuss the system we are developing and several set of results. [Preview Abstract] |
Saturday, October 11, 2008 9:00AM - 9:12AM |
C1.00006: Non-Destructive Corrosion Detection Using Terahertz Time-Domain Spectroscopy and Imaging Lindsay Owens, Stanley Smith, Doug Petkie, Jason Deibel The objective of this project is to detect corrosion of manufactured metal underneath paint. The system used in this research is a commercial terahertz time-domain spectroscopy and imaging system. THz signals are generated and detected using optical excitation of biased semiconductor antennas with 100 femtosecond pulses from an 800 nm laser. Spectral images were of metal samples were taken at frequencies between 100 GHz and 1 THz using a variety of imaging modalities in both transmission and reflection. Prelimiary imaging data shows a clear distinction between corroded and clean metal concealed underneath a coat of paint. [Preview Abstract] |
Saturday, October 11, 2008 9:12AM - 9:24AM |
C1.00007: FEM Simulation of a Terahertz Metamaterial using Short/Long Metal Wire Pairs Zach Gault, Scott Eilerman, Jason Deibel The goal of our work is to develop a successful metamaterial model with an intended negative index of refraction using a simple metal structure on a dielectric substrate. We have developed a structure consisting of short and long straight-wire pairs with a resonance at 0.1 THz. In order to optimize the design parameters of the metamaterial device, we use finite element method (FEM) simulations. We will show how the frequency-dependent transmission data is evaluated to determine the device's effective index of refraction, as well as discuss efforts to fabricate a THz metamaterial device and characterize it using terahertz time-domain spectroscopy. [Preview Abstract] |
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