Fabrication and Characterization of Fast TESs With Small Area for Single Photon Counting

Abstract

Transition edge sensors (TESs) with high energy resolution (ΔE) at telecommunication wavelengths have been realized in the last years for application to experiments of quantum optics and quantum information. In these fields, lasers with repetition rate of the order of 50 MHz are usually applied and hence TES with recovery times lower than 20 ns would be desirable. To this aim, Ti TESs with area ranging between 1 μm × 1 μm and 2 μm × 2 μm are fabricated and characterized, to study the effects of the different sizes of active areas and critical temperatures on the energy resolutions and on the response times. Titanium TESs have been fabricated by thermal evaporation and Electron Beam Lithography technique onSi/SiN substrates, and they have been electrically and optically characterized. The experimental data have been analyzed and correlated to the detector geometrical parameters. The superconducting transitions of TESs with areas down to 1 μm × 1 μm result to be affected by lateral proximity effects of Nb wirings. Ti TESs with critical temperature of 470 mK show response time of about 150 ns and energy resolution of 0.16 eV.

Aluminum–Titanium Bilayer for Near-Infrared Transition Edge Sensors

“…The inset of Figure 5 shows the single photon averaged pulse (dots). The fit obtained by a double exponential equation [ 18 ] provides the response time constant of τ = 2.31 µs, close to the value obtained by the theoretical estimation. The areas under the averaged photon pulses represent the collected energy, E col .…”

A design for an electromagnetic filter for precision energy measurements at the tritium endpoint

“…The target resolution of the combined measurement is 0.05 eV, corresponding to the largest neutrino mass difference 3 measured through oscillation experiments. A reference for the performance of the energy resolution of the calorimeter under development for PTOLEMY is found here [19].…”

Reduced Active Area in Transition-Edge Sensors for Visible-NIR Photon Detection: A Comparison of Experimental Data and Two-Fluid Model

“…The electrodes were fabricated by lift-off of 40 nm sputtered niobium films. Before the Nb deposition, Ti film surface was sputter-cleaned to reduce the contact resistance between Nb and Ti [18].…”

“…It is also well known that the best way to obtain α and β is the impedance measurement, but it is very difficult to perform such technique for frequencies higher than 250 kHz [24]. We can only estimate β from the electrical time constant of the single photon pulse τel=L/[Rsh+R0(1+β)]=145 ns [18], where L is the total inductance of the bias circuit, R0=0.34 Ω and Rsh=20 mΩ are the operating and the shunt resistance, respectively. Though it is difficult to accurately estimate L, due to the parasitic inductance, we can estimate β<2 that is much smaller than the limit β=20 @ R0/Rn=0.05 [23].…”