9 September 1999 Near-field phenomena observed with terahertz pulses
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Proceedings Volume 3828, Terahertz Spectroscopy and Applications II; (1999) https://doi.org/10.1117/12.361042
Event: Industrial Lasers and Inspection (EUROPTO Series), 1999, Munich, Germany
Abstract
Propagation of free-space femtosecond THz pulses (T rays) through and past metal structures with dimension on the order of a wavelength has been studied. In waveguides with diameters close to one wavelength, it is found that the phase velocity can become superluminal and even infinite or negative. T rays that propagate past a 100-micrometers metal wire are delayed when the polarization is perpendicular and advanced when it is parallel. In this case, it is also observed that the centroid velocity can become superluminal. Many of the result do not conform to simple waveguide theory, because of multiple reflections of the evanescent waves inside the waveguide. This 'Fabry-Perot' effect for evanescent waves is the cause of the negative phase velocities below the waveguide cutoff.
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Klaas Wynne, Klaas Wynne, John Carey, John Carey, Justyna Zawadzka, Justyna Zawadzka, Dino A. Jaroszynski, Dino A. Jaroszynski, } "Near-field phenomena observed with terahertz pulses", Proc. SPIE 3828, Terahertz Spectroscopy and Applications II, (9 September 1999); doi: 10.1117/12.361042; https://doi.org/10.1117/12.361042
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