title: Aluminum-Titanium Bilayer for Near-Infrared Transition Edge Sensors.
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.
authors.affiliation: Istituto Nazionale di Ricerca Metrologica, St. delle Cacce 91, Torino 10135, Italy. l.lolli@inrim.it.
authors.forename: Lapo
authors.initials: L
authors.lastname: Lolli
authors.affiliation: Istituto Nazionale di Ricerca Metrologica, St. delle Cacce 91, Torino 10135, Italy. e.taralli@inrim.it.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Taralli
authors.affiliation: Istituto Nazionale di Ricerca Metrologica, St. delle Cacce 91, Torino 10135, Italy. c.portesi@inrim.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Portesi
authors.affiliation: Istituto Nazionale di Ricerca Metrologica, St. delle Cacce 91, Torino 10135, Italy. m.rajteri@inrim.it.
authors.forename: Mauro
authors.initials: M
authors.lastname: Rajteri
authors.affiliation: Istituto Nazionale di Ricerca Metrologica, St. delle Cacce 91, Torino 10135, Italy. e.monticone@inrim.it.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Monticone
keywords: optics; photon counting detector; superconductivity