Thermal coupling effect on the AC thermal signal and DC characteristics ofhigh-temperature superconducting bolometers

In a high-temperature superconducting (HTSC) bolometer, the irradiated ther mal energy is absorbed by the film and finally drained to the heat sink. Th e intensity of the thermal signal depends on the level of the AC irradiatio n energy accumulated. It is usually expected that the magnitude of AC therm al signal is enhanced by weakening the thermal coupling of the bolometer to the heat sink. However, in this study, we found that the AC thermal signal . DeltaT/W-D, was not enhanced but was depressed by weakening the thermal c oupling of the setup. This could be attributed to the nature of the low dis sipation ability in the weak thermal coupling configuration which accumulat ed a higher level of DC Joule heat and gave rise to a huge temperature grad ient between the him and the heat sink. As a result, the heat dissipation w as sped up and the AC thermal signal, DeltaT/W-D, was depressed. Even thoug h the AC thermal signal was lower in the weak thermal coupling configuratio n than in the strong one, the optimum operation condition, where maximum De ltaT/W-D was exhibited. was located in the lower bias current region. This has the advantage of enabling the weak thermal coupling configuration to be operated in a lower-power consumption region.