Quasi-optical techniques have been used to efficiently couple freely propagating subpsec pulses of THz electromagnetic radiation into rectangular metal waveguides. We have observed dispersive, low-loss propagation over the frequency band from 0.65 to 3.5 THz with typical waveguide cross-section dimensions of the order of 250 µm and lengths of 25 mm. We demonstrate both theoretically and experimentally that it is possible to achieve efficient TE10 single-mode coupling and propagation in a suitably sized rectangular waveguide for an incoming focused, linearly polarized THz pulse with a bandwidth covering many octaves in frequency and overlapping more than 35 waveguide modes. The possible applications enabled by these results will be discussed.
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