Far- and near-field photon noise limits to the detectivity of nanometer-thick thermal detectors

Abstract

Thermal-radiation detectors such as bolometers -- often found as thin, suspended films -- are intrinsically limited by their optical absorption properties and by their intrinsic thermal conductive and radiative losses. We analyze the impact of the photon energy exchange between the film and a substrate located close to each other, noticing that the associated near-field exchange has been overlooked and could reduce the detectivity. In addition, we study how the nanometric thickness of the suspended film and its material impact the detectivity of such sensors. It is found that the blackbody-related photon noise limit of the detectivity can be surpassed with thin films. These results emphasize pathways for improvements of thermal-radiation detectors.