A quasi-optical technique for characterizing micromachined waveguides is demonstrated with wideband time-resolved terahertz spectroscopy. A transfer-function representation is adopted for the description of the relation between the signals in the input and output port of the waveguides. The time-domain responses were discretized, and the waveguide transfer function was obtained through a parametric approach in the <i>z</i> domain after describing the system with an autoregressive with exogenous input model. The <i>a priori</i> assumption of the number of modes propagating in the structure was inferred from comparisons of the theoretical with the measured characteristic impedance as well as with parsimony arguments. Measurements for a precision WR-8 waveguide-adjustable short as well as for G-band reduced-height micromachined waveguides are presented.
© 2003 Optical Society of America
(230.7370) Optical devices : Waveguides
(300.6270) Spectroscopy : Spectroscopy, far infrared
(310.6870) Thin films : Thin films, other properties
(320.5540) Ultrafast optics : Pulse shaping
(350.4010) Other areas of optics : Microwaves
Sillas Hadjiloucas, Roberto K. H. Galvão, John W. Bowen, Rainer Martini, Martin Brucherseifer, Harm P. M. Pellemans, Peter Haring Bolívar, Heinrich Kurz, John Digby, Geoffrey M. Parkhurst, and J. Martyn Chamberlain, "Measurement of propagation constant in waveguides with wideband coherent terahertz spectroscopy," J. Opt. Soc. Am. B 20, 391-401 (2003)