The electric field intensity of the THz radiation from YBCO thin films excited by ultrashort laser pulses has been enhanced by a factor of 3 using a-axis oriented films instead of c-axis oriented ones used previously under the same excitation conditions. This corresponds to the enhancement of a factor of 10 for the radiation power. From the transmittance measurements of the millimeter wave for a-and c-axis oriented films, the origin of the enhancement is attributed to the increased fraction of the THz electromagnetic wave power transmitted from the YBCO film to free space. This result indicates that the utilization of the anisotropic properties of high-Tc superconductors is effective to enhance the radiation power.

The DC resistivities of silicon germanium thin films on Si substrates by a non-contact and non-destructive technique using terahertz time domain spectroscopy (THz-TDS) agree with the values obtained by the four-point probe measurement. In the present experiment, the mobility has not been precisely determined owing to the limitation of the frequency range in our equipment (from 0.1 to 1.5 THz). However, when the mobility becomes large enough, this method will be highly useful in evaluating semiconductor thin films, since the method gives the same data as those from Hall measurement without sample processing or electrode contact to sample.