Photon Detection - superconducting detectors

1-presentation

The goals of this project are the fabrication and the characterisation of superconducting photons counters. These bolometric photo-detectors are made of an ultrathin (<10 nm) film of superconducting material, whose properties are altered by the absorption of a single photon. The expected behaviour makes them very attractive for application in photonic quantum information, such as quantum cryptography and all-optical quantum logic gates. These detectors should exhibit better quantum efficiencies and dark counts than currently available photons counters at telecom wavelength (1.3 and 1.55 microns). [Verevkin]. Furthermore they should offer the possibilities of non-linear detection and photon number resolution.

2- Operating principle

These detectors are made of a superconducting strip of a few microns long, 250 nm wide and 6 nm thick. At the temperature of liquid helium (4K), the strip (usually in NbN that has a critical temperature Tc=10 K) is biased by a current just below the critical current. The absorption of a photon by the strip rises locally its temperature. This creates a non-superconducting hot spot [Kadin]. The current is then forced to flow around this hot spot and the current density can then reach the critical current. The strip becomes resistive and a short (30 ps) voltage pulse appears across the strip.

3-Properties

Depending on the gap between the current bias and the critical current, the superconducting-normal transition can require the absorption of one or several photons. A non-linear photo-detector sensitive to more-than-two photon pulses can then be realized [Gol’tsman]. This property offers interesting possibilities for original quantum optics experiments Furthermore, it appears that the electrical pulse shape in the linear regime depends on the energy of the light deposited on the film and therefore on the number of photons [Gol’tsman].  We have shown that these detectors can be very fast and exhibit jitter as low as 16 ps [Tarkhov].

4- technology

The epitaxial growth of ultrathin NbN film (<10 nm) is carried out at CEA Grenoble by J.C. Villegier et al on sapphire or MgO at 600°C. The 250 nm stripe etching is done by reactive ion etching (RIE) [Villegier, Romestain,Maingault] or by local oxidation with an atomic force microscope [Delacour].   To improve the quantum efficiency of these detectors, the reflection and transmission coefficients can be tailored by 2D or 3D light confinement techniques to enhance the photon absorption probability. These techniques (cavities, plasmons) [Glass] have been widely used for semi-conducting detectors. These aspects are done in collaboration with CEA-LETI in Grenoble and P. Lalanne (LCFIO) in Orsay.

Sponsors 

European project « Single-photon nanostructured detectors for advanced optical applications » (SINPHONIA), www.sinphonia.org (2006-2008)

References

- A.M Glass et al, “Periodically structured amorphous silicon detectors with improved picsecond responsivity” Appl ; Phys ; Lett. 44, 77 (1984).
- G.N.Gol’tsman et al, “Picosecond superconducting single-photon optical detector”, Appl. Phys. Lett. 79, 705 (2001).
- A.M. Kadin et M.W. Johnson, “Nonequilibrium photon-induced hotspot : a new mechanism for photodetection in ultrathin metallic films”, Appl. Phys. Lett. 69, 3938 (1996). 
- A. Verevkin et al, “Detection efficiency of large-active-area NbN single-photon superconducing detectors in the ultraviolet to near-infrared range”, Appl. Phys. Lett. 80, 4687 (2002).

Our publications

- J-C Villegier et al, "New developments in textured and epitaxial NbN superconducting layers for ultimate sensors and RSFQ digital circuits", J. Phys. IV France 12, Pr3-129, (2002).
- R. Romestain, B. Delaet, P. Renaud-Goud, I. Wang, C. Jorel, J.-C. Villegier, J.-Ph. Poizat, “Superconducting niobium nitride hot electron bolometer for single photon counting”, New J. Phys. 6, 129 (2004).
- C. Delacour, J. Claudon, J.-Ph. Poizat, B. Pannetier, and V. Bouchiat, R. Espiau de Lamaestre, J.-C. Villegier, M. Tarkhov, A. Korneev, B. Voronov, and G. Gol’tsman, « Superconducting single photon detectors made by local oxidation with an atomic force microscope”, Appl. Phys. Lett. 90, 191116 (2007)
- M. Tarkhov, J. Claudon, J. Ph. Poizat, A. Korneev, A. Divochiy, O. Minaeva, V. Seleznev, N. Kaurova, B. Voronov, A.V. Semenov, and G. Gol’tsman, « Ultrafast reset time of Superconducting Single Photon Detectors », Appl. Phys. Lett. 92, 241112 (2008)
- L. Maingault,1, M. Tarkhov, I. Florya, A. Semenov, R. Espiau de Lamaëstre, P. Cavalier, G. Gol’tsman, J.-P. Poizat, and J.-C. Villégier, “Spectral dependency of superconducting single photon detectors”, Journal of Applied Physics 107, 116103 (2010).

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