A bolometer is described. A bolometer includes a superconductor-insulator-semiconductor-superconductor structure or a superconductor-insulator-semiconductor-insulator-superconductor structure. The semiconductor comprises an electron gas in a layer of silicon, germanium or silicon-germanium alloy in which valley degeneracy is at least partially lifted. The insulator or a one or both of the insulators may comprise a layer of dielectric material. The insulator or a one or both of the insulators may comprise a layer of non-degenerately doped semiconductor.