NOVEL TERAHERTZ RADIATION FROM FLUX-TRAPPED YBA2CU3O7-DELTA THIN-FILMS EXCITED BY FEMTOSECOND LASER-PULSES

We discovered a pew type of terahertz (THz) radiation from YBa2Cu3O7-d elta thin films. Ultrashort electromagnetic pulses, which are referred to as THz radiation, were emitted into free space by irradiating the superconductive films with femtosecond laser pulses. The THz radiation , with a spectrum extending from 0.1 to 3 THz, was excited in both the films applied with a magnetic field and the flux-trapped films. The r esults suggest that the screening current for the external magnetic fi eld and circulating current around the trapped Bur play an important r ole in the emission mechanism.