Ultra-fast superconducting single photon detectors

Ultra-fast superconducting single photon detectors

Superconducting single photon detector (SSPD) technology has emerged as a building block for numerous applications, including quantum communication, optical quantum computing or space to ground communication [1] . Such devices are made of a long superconducting nanowire (typically 100nm wide and several µm long) biased just below its critical current. When an incident photon is absorbed by the nanowire, it generates a hot spot, which locally destroys the superconductivity and creates a resistive region [2] (figure 1). This phenomenon induces a measurable pulse voltage (typical duration 5 ns) that is used to detect the arrival of a single photon, before the nanowire returns to its initial state.

Figure 1 : Basic operation principal of the superconducting single-photon detector (SSPD) : a schematic illustrating the detection cycle.
(i) The superconducting nanowire biased just below the critical current.
(ii) Creation of the hotspot as a photon is absorbed.
(iii and iv) Formation of a resistive barrier across the width of the nanowire2.
(v) Growth of the resistive region along the axis of the nanowire.
(vi) Reset to the superconducting state.

Based on that principle, single photon detection started a decade ago using mainly Nb and NbN nanowires that operate in liquid He (4K). However, the speed of these devices is limited by the reset time which is intrinsically set by the electron-phonon scattering time of the superconductor. In addition, the constraint of the low temperature slows down the development of most of the practical applications. In this context the use of High-Tc Superconducting nanowires presents two main advantages: the critical temperature of the superconducting state is higher and the electron-phonon scattering time is much shorter than the actual SSPD ones, therefore enabling a faster operation.
Our team at ESPCI-ParisTech has developed a powerful technique to structures High-Temperature Superconducting films at the nanoscale combining advanced electron-beam lithography with ion irradiation technique [3]. We have been able to produce reliable sub-micron wide nanowires, which are the main ingredient to build SSPD. This project aims to develop a new kind of ultra-fast superconducting nanowire single-photon detectors using YBa2Cu3O7 material. Nanofabrication will be carried out using an electron beam lithography facility at ENS. Then the devices will be electrically characterized at low frequency and microwave frequency using a close cycle refrigerator. In a second step, the device will be operated as a SSPD using photons delivered by a laser connected to an optical fiber.

[1] Nature Photon. 3 696–705 (2009), [2] Appl. Phys. Lett. 79, 705–707 (2001), [3] Appl. Phys. Lett. 87, 102502 (2005), J. Appl. Phys. 102, 083903 (2007), Appl. Phys. Lett. 89, 112515 (2006).

Permanents :

  • cheryl.palma at espci.fr - Tel : 01 40 79 45 71