ENHANCED THZ RADIATION FROM YBCO USING A-AXIS ORIENTED THIN-FILMS EXCITED BY ULTRASHORT OPTICAL PULSES

The electric field intensity of the THz radiation from YBCO thin films excited by ultrashort laser pulses has been enhanced by a factor of s imilar to 3 using a-axis oriented films instead of c-axis oriented one s used previously under the same excitation conditions. This correspon ds to the enhancement of a factor of 10 for the radiation power. From the transmittance measurements of the millimeter wave for a- and c-axi s oriented films, the origin of the enhancement is attributed to the i ncreased fraction of the THz electromagnetic wave power transmitted fr om the YBCO film to free space. This result indicates that the utiliza tion of the anisotropic properties of high-T-c superconductors is effe ctive to enhance the radiation power.