| Scope and method of study. In this study, two planar waveguides, the dielectric slab waveguide and the parallel-plate metal waveguide, were investigated via the propagation of input subps pulses, for the use of technical and fundamental research applications in the THz frequency range. All of the experimentally observed features were explained in detail using classical waveguide theory and quasi-optical theory. The crux of the data analysis was carried out in the frequency-domain, by transforming the time-domain data into the frequency-domain using the Discrete Fourier Transform.; Findings and conclusions. Highly dispersive, low-loss, single TM0 mode propagation, along with efficient quasi-optic coupling, was observed for two dielectric slab waveguides, within the bandwidth from 0.2 to 3.5 THz. The waveguides were made of high-density polyethylene and had nominal dimensions of 150 μm thick by 10 MM long, and 120 μm thick by 20 mm long. The high group velocity dispersion (CVD) associated with the slab waveguides caused extensive pulse broadening, resulting in positively chirped output pulses. The solution to the excessive pulse broadening is the TEM mode of the parallel-plate metal waveguide, which has ideally zero GVD and also a simple field pattern that enables efficient quasi-optic coupling. This WAS demonstrated using two parallel-plate copper waveguides, both having a plate separation of 108 μm, one 12.6 mm long and the other 24.4 mm long. Undistorted, low-loss propagation of input 0.3 ps FWHM pulses was observed within the bandwidth from 0.2 to 4 THz, thereby for the first time, realizing the ideal THz interconnect. This concept was tested further in the form of a physically flexible, practicable interconnect with a propagation length as large as 0.25 m. A final theoretical study that focused on deriving the absorption spectra of thin dielectric films using the above planar waveguides substantiated a powerful THz technology, Guided-Wave THz-TDS. It was predicted that the dielectric slab waveguide could be used to measure absorption of samples two orders of magnitude less absorbent, than would be possible with a single-pass transmission measurement; a highly sensitive evanescent field sensor. |
