THz time-domain spectroscopy of high T_c substrates

Using the method of time-domain spectroscopy, we have measured the absorption and dispersion from 0.2 to 2 THz of the high Tc substrates, magnesium oxide, yttria-stabilized zirconia (YSZ), and lanthanum aluminate. Our measurements on YSZ and LaAlO3 at both room temperature and 85 K show unacceptably large absorptions for high-speed transmission line applications. At 85 K, MgO is shown to be an excellent material in terms of its low loss at THz frequencies.