Nonbolometric optical response of YBa2Cu3O7-epitaxial films

The optical response of high-quality epitaxial YBa2Cu3O7- films on LaGaO3 and SrTiO3 substrates is reported. A careful analysis of the results reveals a strong nonbolometric response at temperatures below the onset of the superconducting transition. This finding is in contrast with recently published reports which attribute the optical response of epitaxial films to a bolometric effect only. We interpret this response as due to photoenhanced flux creep in the superconducting films. © 1989 The American Physical Society.