THERMAL-MODEL FOR THE BOLOMETRIC RESPONSE OF HIGH-TC SUPERCONDUCTING FILMS TO OPTICAL PULSES

The voltage response of thin-film high T(c) superconductors to electromagnetic radiation is the basis for highly promising optical detectors. Experiments with laser pulses have created a controversy over whether the observed responses are due to a thermal mechanism or caused by a non-equilibrium process. In part, this controversy was caused by inadequate thermal modelling of the bolometric response. The present study applies a rigorous thermal radiation and heat conduction analysis to a high T(c) film irradiated by an optical pulse and compares the predicted bolometric voltage response to experimental data. Based on the assumption of thermal boundary resistance between film and substrate as predicted by acoustic mismatch theory, the calculated temperature increase for 200 ns pulses is not sufficient to account for the observed voltage response when the initial film temperature is well below the transition temperature.