Ultrafast optoelectronic switches based on high-T/sub c/ superconductors

We present measurements of the ultrafast reflectivity change of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films upon femtosecond laser excitation. The response is attributed to the breaking of Cooper pairs and the subsequent recombination of quasiparticles. In a current-biased superconducting bridge, these transient processes lead to the generation of picosecond electromagnetic pulses, which can be directly detected by measuring the emitted radiation from the bridge in a quasi-optical setup. We show that the emitted pulse can be calculated from the all-optical measurements.