Single photon detection in NbRe superconducting microstrips

Abstract

Detection of single infrared photons in superconducting microstrips of 4 nm thick disordered Nb0.15Re0.85 has been investigated. Microstrips with a critical temperature of 5.15 K and widths from 1.0 to 2.5 μm have been fabricated by optical lithography. We demonstrate single photon detection sensitivity at 1.5 μm wavelength at a temperature of 1.79 K. By investigating the detection process at this temperature, we find that the current bias threshold is at 21% of the depairing current. This threshold is similar to what should be observed in typical amorphous superconductors, which confirms that ultrathin disordered Nb0.15Re0.85 is an interesting material for superconducting microstrip single photon detectors that operate above 1 K.

Investigation of NbRe for superconducting microstrips single photon detectors

“…We have found γ = 15 for the polycrystalline case and γ = 93 for the single-crystal case. By comparing the values of δ and γ in [32], we expect that the detection process in our ultrathin NbRe films is similar to that of a sensitive amorphous superconductor and the single photon sensitivity at 1.5 µm it is possible at a threshold of 0.21JDP [29]. For this reason, we concentrated our analysis only on devices that show this requirement.…”

“…The samples were patterned through optical lithography and argon ion etching. Details of the fabrication process can be found elsewhere [29]. Samples with different nominal widths w ranging from 1 µm to 2.5 µm, and lengths L from 5 µm to 12.5 µm were fabricated.…”

“…The pulses were acquired by an oscilloscope or counted using a counter (Hewlett-Packard 5316B). Further details of the electronic set-up can be found in [29]. , To avoid latching, a phenomenon that occurs when Ib returns too quickly back into the detector and prevents efficient detection, a 470 nH series inductance and a 333 Ω parallel resistor were inserted.…”

Investigation of dark count rate in NbRe microstrips for single photon detection

“…astronomy, free space quantum communication, LIDAR, etc [18][19][20][21][22]. Recently, NbRe was proposed as a promising material for the fabrication of SN(M)SPDs [23][24][25]. NbRebased nanostrips [26] and microstrips [24] have been demonstrated to work as single photon detectors.…”

Optimal configuration of a superconducting photon number resolving detector

“…These can be arranged according to an array, which proved to resolve the number of photons, acting as a PNRD [3]. Different materials and structures to improve the performance of SNSPDs have been investigated [4][5][6][7][8][9][10][11]. However, at 1550 nm, PNRD based on the NbN technology show high efficiency at relative high temperatures (T= 2 K) [3,12].…”