Terahertz Emission Study of Femtosecond Time-Transient Nonequilibrium State in Optically Excited YBa 2Cu 3O 7-δ Thin Films

Abstract
We observed the temperature dependence of a femtosecond time-transient photoresponse in YBa2Cu3O7-δ thin films by detecting terahertz (THz) emission. Ultrashort electromagnetic pulses which are referred to as THz emission were generated by ultrafast supercurrent modulation with femtosecond laser pulse irradiation. The transient response is discussed in relation to the quasiparticle dynamics of the nonequilibrium superconductor.