Fast-Response Superconducting Titanium Bolometric Detectors

High time resolution optical/infrared (IR) astronomy will require fast response detectors. In order to meet such requirement, cryogenic optical/IR detectors, such as superconducting tunnel junctions and transition-edge sensors, are under development. Of these cryogenic detectors, superconducting titanium (Ti) bolometric detectors, with a transition temperature of around 300 mK, based on the electron-phonon decoupling mechanism, are promising in fast response. In this paper, we report on the characterization of electro-thermal properties of a small-size (1 mu m x 1 mu m x 37 nm) superconducting Ti detector. The low-frequency noise of Ti film was fitted by empirical Hooge model. A discrepancy between the Hooge constant of the Ti film and that of normal metals shows disorder in the Ti film. Thermal conductance was extracted via measured current-voltage curves at different bath temperatures. The time constant was calculated as tens of nanoseconds, which was faster than expected. The fast response potentially enables the high-speed optical/IR astronomical observations. Detailed experimental and analytical results are also presented.