TERAHERTZ RADIATION FROM SUPERCONDUCTING YBA2CU3O7-DELTA THIN-FILMS EXCITED BY FEMTOSECOND OPTICAL PULSES

Ultrashort electromagnetic waves (600 fs width) from superconducting Y BCO thin films have been observed by irradiating current-biased sample s with femtosecond optical laser pulses (80 fs width). The Fourier com ponent of the pulse extends up to similar to 2 THz. The characteristic s of the radiation are studied and the radiation mechanism is ascribed to the ultrafast supercurrent modulation by the laser pulses, which i nduce the nonequilibrium superconductivity. (C) 1996 American Institut e of Physics.