Estimating dielectric parameters by reflecting evanescent waves at THz frequencies

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Society of Photo-Optical Instrumentation Engineers (SPIE)
The THz/Far-IR Beamline at the Australian Synchrotron was used to demonstrate a novel method of estimating the dielectric properties of homogenous substances in the 1.0 THz to 4.0 THz region. Attenuated total reflection (ATR) coupled with synchrotron sources allow rapid evaluation of samples. The source is incoherent, thus normally only reflectance can be derived, as phase shift data cannot be obtained with this arrangement. A method is presented of deriving the full complex dielectric parameters by a modified frustrated internal reflection technique which reflects the evanescent wave using a gold plated mirror. Oil and alcohol samples were used in the study. With the mirror in situ, the reflectance changed from being enhanced at some frequencies to undergoing a frequency dependent destructive interference at other frequencies. The change in different samples was noted to vary according to the refractive index (but not the absorption coefficient) of the sample. © (2022) Society of Photo-Optical Instrumentation Engineers (SPIE)
THZ range, ANSTO, Australian organizations, Dielectric properties, Synchrotron radiation sources, Frequency dependence, Absorption
Vilagosh, Z., Foroughimehr, N., Lajevardipour, A., Appadoo, D., Juodkazis, S., & Wood, A. (2021). Estimating dielectric parameters by reflecting evanescent waves at THz frequencies. Paper presented to Biomedical Imaging and Sensing Conference 2021, 20-22 April 2021, Online. In Yatagai, T. (ed). Proceedings Volume 12000, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XV; 120000L (2022). doi:10.1117/12.2609533