Identification of nonbolometric photoresponse in YBa2Cu3O7−δ thin films based on magnetic field dependence

Optically induced transient voltages across a current-biased bridge structure fabricated from an epitaxial YBa2Cu3O7−δ thin film are reported. A novel technique consisting of applying a small magnetic field perpendicular to the sample was used to identify any bolometric contribution to the photoresponse. Comparison to resistance versus temperature curves with and without the field establishes a slow component in the photoresponse as bolometric and unambiguously identifies a fast component as a nonthermal transient.