Interaction of picosecond optical pulses with high T c superconducting films

Infrared pulses (1.06 μm wavelength, ≊150 ps long) from a Nd:YAG laser illuminated a superconducting YBa2Cu3O7 granular film, 0.7 μm thick. This caused the film to switch from the superconducting to the normal (resistive) state in less than 2 ns, followed by a much slower recovery ∼1 μs. The initial fast switching may be explained by nonequilibrium hot-electron energy transfer from the top absorbing layer (≊100 nm thick) through the film, followed by an essentially bolometric response and cooldown via equilibrium thermal conduction out of the film.