Abstract
Transition-edge sensors (TESs) are single photon detectors attractive for applications in quantum optics and quantum information experiments owing to their photon number resolving capability. Nowadays, high-energy resolution TESs for telecommunication are based on either W or Au/Ti films, demonstrating slow recovery time constants. We report our progress on the development of an Al/Ti TES. Since bulk aluminum has a critical temperature (Tc) of ca. 1.2 K and a sufficiently low specific heat (less than 10−4 J/cm3K2), it can be employed to produce the sensitive material for optical TESs. Furthermore, exploiting its high Tc, Al-based TESs can be trimmed in a wider temperature range with respect to Ti or W. A first Al/Ti TES with a Tc ≈ 142 mK, investigated from a thermal and optical point of view, has shown a response time constant of about 2 μs and single photon discrimination with 0.34 eV energy resolution at telecom wavelength, demonstrating that Al/Ti films are suitable to produce TESs for visible and NIR photon counting.
Highlights
A transition-edge sensor is a superconducting phase thermometer, able to detect the number of incident photons through its intrinsic energy resolution capability
The core of a Transition-edge sensors (TESs) is the superconducting thin film: it is biased in its transition region, and, in this way, the film works as a sensitive thermometer measuring the temperature change due to the photon absorption
TESs for IR-visible range have been fabricated using different superconducting materials: single layer-based TESs use tungsten [1], hafnium [2], or titanium [3], whereas bilayer-based TESs use titanium proximized by gold [4], palladium [5], or molybdenum proximized by gold [6]
Summary
A transition-edge sensor is a superconducting phase thermometer, able to detect the number of incident photons through its intrinsic energy resolution capability. The core of a TES is the superconducting thin film: it is biased in its transition region, and, in this way, the film works as a sensitive thermometer measuring the temperature change due to the photon absorption. In superconducting and normal metal bilayer thin films, the critical temperature can be theoretically trimmed from 0 to the Tc of the bulk superconductor by changing the layer thickness ratio [7]. In this way, it is possible to control the most important characteristics of a TES detector [8]
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