A YBaCuO-BiSb photo-thermoelectric sensor: mathematical modeling of normalised detectivity

In this paper a mathematical modeling of the design of a YBaCuO-BiSb photo-thermoelectric sensor based on equilibrium superconductivity is presented. The design is such that in addition to the heat transferred to the substrate by conduction, it includes thermoelectric heat transfer to the cold junction of the thermocouple. Heat dissipation by the sensitive area of the sensor to the liquid nitrogen environment by radiation also forms part of the thermal equilibrium. The standard mathematical relationship between the noise equivalent power (NEP), responsivity (S) and the noise equivalent voltage (NEV) is used to develop a theoretical expression for the normalised detectivity of the sensor. The expression is then developed in terms of the thermoelectric figure of merit of the thermocouple. An illustration as a plot of the detectivity over the transition width 80-90 K of the superconductor YBCO is included in the paper