Conductivity artifacts in optical-pump THz-probe measurements of YBa2Cu3O7

Transient changes in the complex conductivity of the high-temperature superconductor YBa2Cu3O7 have been measured with optical-pump THz-probe spectroscopy. Artifacts in the conductivity arise when optical excitation induces changes in the material response that occur on a time scale comparable with or faster than the THz pulse width. A model is presented that agrees with experiments and provides insight in distinguishing between artifacts and real features in transient conductivity measurements. (C) 2000 Optical Society of America [S0740-3224(00)01102-4].