SPECTROSCOPY WITH ELECTRONIC TERAHERTZ TECHNIQUES FOR CHEMICAL AND BIOLOGICAL SENSING

Abstract

By illuminating the sample with a broadband 10-500 GHz stimulus and coherently detecting the response, we obtain reflection and transmission spectra of common powdered substances, and compare them as a starting point for distinguishing concealed threats in envelopes and on personnel. Because these samples are irregular and their dielectric properties cannot be modulated, the spectral information we obtain is largely qualitative. To show how to gain quantitative information on biological species at micro- and millimeter-wave frequencies, we introduce thermal modulation of a globular protein in solution, and show that changes in microwave reflections coincide with accepted visible absorption spectra, pointing the way toward gaining quantitative chemical and biological spectra from broadband terahertz systems.