The THz Hot-Electron Photon Counter Concept

A document proposes the development of hot-electron photon counters (HEPCs) for detecting terahertz photons in spaceborne far-infrared astronomical instruments. These would be superconducting-transition-edge devices: they would contain superconducting bridges that would have such low heat capacities that single terahertz photons would cause transient increases in their electron temperatures through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. Single devices or imaging arrays of the devices would be fabricated as submicron-sized bridges made from films of disordered Ti (which has a superconducting-transition temperature of ≈0.35 K) between Nb contacts on bulk silicon or sapphire substrates. In operation, these devices would be cooled to a temperature of ≈0.3 K. The proposed devices would cost less to fabricate and operate, relative to integrating bolometers of equal sensitivity, which must be operated at a temperature of ≈0.1 K.