Modelization and experiments on high Tc superconducting bolometers in the 10-90 K range of temperature

As previously reported, the critical current Ic dependence versus optical power P in the mW range at 780 nm, with P focused on microbridges of YBCO thin films,can be calculated using simple assumptions on heat production in the superconducting film and heat conduction to the substrate. For the model was only valid on a limited range of temperature T where the thermal boundary resistance Rbd lying at the film-substrate interface could be taken as a constant R0 = 10-3 K cm2/W, we present a full model obtained by integration of the coupled Fourier equations of the temperature in the superconducting anisotropic YBCO film and in its substrate. We show that the thermal boundary resistance modelized as Rbd(T) = B/T3 + R0, with B/T3 given by the acoustic mismatch model, is still limiting the heat transfer from the film to the substrate at least down to 10 K. As a consequence, the simple model that uses only Rbd(T) and dIc/dT is still useful and allows realistic evaluations of the current sensitivity Sl(P, T) to the applied power P on the temperature range 10-90 K. Calculated Sl(p, T) in the 0.1-1 A/W range agree well with those measured on YBCO/MgO or YBCO/SrTiO3 devices. (orig.)