|
|
Słysz W, Węgrzecki M, Bar J, Grabiec P, Górska M, Zwiller V, et al. Fiber-coupled single-photon detectors based on NbN superconducting nanostructures for practical quantum cryptography and photon-correlation studies. Appl Phys Lett. 2006;88(26):261113 (1 to 3).
Abstract: We have fabricated and tested a two-channel single-photon detector system based on two fiber-coupled superconducting single-photon detectors (SSPDs). Our best device reached the system quantum efficiency of 0.3% in the 1540-nm telecommunication wavelength with a fiber-to-detector coupling factor of about 30%. The photoresponse consisted of 2.5-ns-wide voltage pulses with a rise time of 250ps and timing jitter below 40ps. The overall system response time, measured as a second-order, photon cross-correlation function, was below 400ps. Our SSPDs operate at 4.2K inside a liquid-helium Dewar, but their optical fiber inputs and electrical outputs are at room temperature. Our two-channel detector system should find applications in practical quantum cryptography and in antibunching-type quantum correlation measurements.
The authors would like to thank Dr. Marc Currie for his assistance in early time-resolved photoresponse measurements and Professor Atac Imamoglu for his support. This work was supported by the Polish Ministry of Science under Project No. 3 T11B 052 26 (Warsaw), RFBR 03-02-17697 and INTAS 03-51-4145 grants (Moscow), CRDF Grant No. RE2-2531-MO-03 (Moscow), RE2-2529-MO-03 (Moscow and Rochester), and US AFOSR FA9550-04-1-0123 (Rochester). Additional funding was provided by the grants from the MIT Lincoln Laboratory and BBN Technologies Corp.
|
|
|
|
Słysz W, Wegrzecki M, Bar J, Grabiec P, Górska M, Zwiller V, et al. Fibre-coupled, single photon detector based on NbN superconducting nanostructures for quantum communications. J Modern Opt. 2007;54(2-3):315–26.
Abstract: We present a novel, two-channel, single photon receiver based on two fibre-coupled, NbN, superconducting, single photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders and are known for ultrafast and efficient detection of visible-to-infrared photons. Coupling between the NbN detector and optical fibre was achieved using a micromechanical photoresist ring placed directly over the SSPD, holding the fibre in place. With this arrangement, we obtained coupling efficiencies up to ∼30%. Our experimental results showed that the best receiver had a near-infrared system quantum efficiency of 0.33% at 4.2 K. The quantum efficiency increased exponentially with the photon energy increase, reaching a few percent level for visible-light photons. The photoresponse pulses of our devices were limited by the meander high kinetic inductance and had the rise and fall times of approximately 250 ps and 5 ns, respectively. The receiver's timing jitter was in the 37 to 58 ps range, approximately 2 to 3 times larger than in our older free-space-coupled SSPDs. We stipulate that this timing jitter is in part due to optical fibre properties. Besides quantum communications, the two-detector arrangement should also find applications in quantum correlation experiments.
|
|
|
|
Vachtomin YB, Antipov SV, Maslennikov SN, Smirnov KV, Polyakov SL, Kaurova NS, et al. Noise temperature measurements of NbN phonon-cooled hot electron bolometer mixer at 2.5 and 3.8 THz. In: Proc. 15th Int. Symp. Space Terahertz Technol. Northampton, Massachusetts, USA; 2004. p. 236–41.
Abstract: We present the results of noise temperature measurements of NbN phonon-cooled HEB mixers based on a 3.5 nm NbN film deposited on a high-resistivity Si substrate with a 200 nm – thick MgO buffer layer. The mixer element was integrated with a log-periodic spiral antenna. The noise temperature measurements were performed at 2.5 THz and at 3.8 THz local oscillator frequencies for the 3 µm x 0.2 µm active area devices. The best uncorrected receiver noise temperatures found for these frequencies are 1300 K and 3100 K, respectively. A water vapour discharge laser was used as the LO source. We also present the results of direct detection contribution to the measured Y-factor and of a possible error of noise temperature calculation. This error was more than 8% for the mixer with in-plane dimensions of 2.4 x 0.16 µm 2 at the optimal noise temperature point. The use of a mesh filter enabled us to avoid the effect of direct detection and decrease optical losses by 0.5 dB. The paper is concluded by the investigation results of the mixer polarization response. It was shown that the polarization can differ from the circular one at 3.8 THz by more than 2 dB.
|
|
|
|
Vachtomin YB, Antipov SV, Maslennikov SN, Smirnov KV, Polyakov SL, Zhang W, et al. Quasioptical hot electron bolometer mixers based on thin NBN films for terahertz region. In: Proc. 16th Int. Crimean Microwave and Telecommunication Technology. Vol 2.; 2006. p. 688–9.
Abstract: Presented in this paper are the performances of HEB mixers based on 2-3.5 nm thick NbN films integrated with log-periodic spiral antenna. Double side-band receiver noise temperature values are 1300 K and 3100 K at 2.5 THz and at 3.8 THz, respectively. Mixer gain bandwidth is 5.2 GHz. Local oscillator power is 1-3 muW for mixers with different active area
|
|
|
|
Vachtomin YB, Antipov SV, Kaurova NS, Maslennikov SN, Smirnov KV, Polyakov SL, et al. Noise temperature, gain bandwidth and local oscillator power of NbN phonon-cooled HEB mixer at terahertz frequenciess. In: Proc. 29th IRMMW / 12th THz. Karlsruhe, Germany; 2004. p. 329–30.
Abstract: We present the performances of HEB mixers based on 3.5 nm thick NbN film integrated with log-periodic spiral antenna. The double side-band receiver noise temperature values are 1300 K and 3100 K at 2.5 THz and at 3.8 THz, respectively. The gain bandwidth of the mixer is 4.2 GHz and the noise bandwidth is 5 GHz. The local oscillator power is 1-3 /spl mu/W for mixers with different active area.
|
|
|
|
Vahtomin YB, Finkel MI, Antipov SV, Voronov BM, Smirnov KV, Kaurova NS, et al. Gain bandwidth of phonon-cooled HEB mixer made of NbN thin film with MgO buffer layer on Si. In: Harvard university, editor. Proc. 13th Int. Symp. Space Terahertz Technol. Cambridge, MA, USA; 2002. p. 259–70.
Abstract: We present recently obtained values for gain bandwidth of NbN HEB mixers for different substrates and film thicknesses and for MgO buffer layer on Si at LO frequency of 0.85-1 THz. The maximal bandwidth, 5.2 GHz, was achieved for the device on MgO buffer layer on Si with a 2 nm thick NbN film. Functional devices based on NbN films of such thickness were fabricated for the first time due to an improvement of superconducting properties of NbN film deposited on MgO buffer layer on Si substrate.
|
|
|
|
Vakhtomin YB, Finkel MI, Antipov SV, Smirnov KV, Kaurova NS, Drakinskii VN, et al. The gain bandwidth of mixers based on the electron heating effect in an ultrathin NbN film on a Si substrate with a buffer MgO layer. J of communications technol & electronics. 2003;48(6):671–5.
Abstract: Measurements of the intermediate frequency band 900 GHz of mixers based on the electron heating effect (EHE) in 2-nm- and 3.5-nm-thick superconducting NbN films sputtered on MgO and Si substrates with buffer MgO layers are presented. A 2-nm-thick superconducting NbN film with a critical temperature of 9.2 K has been obtained for the first time using a buffer MgO layer.
|
|
|
|
Vasilev DD, Malevannaya EI, Moiseev KM, Zolotov PI, Antipov AV, Vakhtomin YB, et al. Influence of deposited material energy on superconducting properties of the WSi films. In: IOP Conf. Ser.: Mater. Sci. Eng. Vol 781.; 2020. 012013 (1 to 6).
Abstract: WSi thin films have the advantages for creating SNSPDs with a large active area or array of detectors on a single substrate due to the amorphous structure. The superconducting properties of ultrathin WSi films substantially depends on their structure and thickness as the NbN films. Scientific groups investigating WSi films mainly focused only on changes of their thickness and the ratio of the components on the substrate at room temperature. This paper presents experiments to determine the effect of the bias potential on the substrate, the temperature of the substrate, and the peak power of pulsed magnetron sputtering, which is the equivalent of ionization, a tungsten target, on the surface resistance and superconducting properties of the WSi ultrathin films. The negative effect of the substrate temperature and the positive effect of the bias potential and the ionization coefficient (peak current) allow one to choose the best WSi films formation mode for SNSPD: substrate temperature 297 K, bias potential -60 V, and peak current 3.5 A.
|
|
|
|
Verevkin AA, Pearlman A, Slysz W, Zhang J, Sobolewski R, Chulkova G, et al. Ultrafast superconducting single-photon detectors for infrared wavelength quantum communications. In: Donkor E, Pirich AR, Brandt HE, editors. Proc. SPIE. Vol 5105. SPIE; 2003. p. 160–70.
Abstract: We have developed a new class of superconducting single-photon detectors (SSPDs) for ultrafast counting of infrared (IR) photons for secure quantum communications. The devices are operated on the quantum detection mechanism, based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The detectors are fabricated from 3.5-nm-thick NbN films and they operate at 4.2 K inside a closed-cycle refrigerator or liquid helium cryostat. Various continuous and pulsed laser sources have been used in our experiments, enabling us to determine the detector experimental quantum efficiency (QE) in the photon-counting mode, response time, time jitter, and dark counts. Our 3.5-nm-thick SSPDs reached QE above 15% for visible light photons and 5% at 1.3 – 1.5 μm infrared range. The measured real-time counting rate was above 2 GHz and was limited by the read-out electronics (intrinsic response time is <30 ps). The measured jitter was <18 ps, and the dark counting rate was <0.01 per second. The measured noise equivalent power (NEP) is 2 x 10-18 W/Hz1/2 at λ = 1.3 μm. In near-infrared range, in terms of the counting rate, jitter, dark counts, and overall sensitivity, the NbN SSPDs significantly outperform their semiconductor counterparts. An ultrafast quantum cryptography communication technology based on SSPDs is proposed and discussed.
|
|
|
|
Verevkin AA, Ptitsina NG, Smirnov KV, Gol'tsman GN, Voronov BM, Gershenzon EM, et al. Hot electron bolometer detectors and mixers based on a superconducting-two-dimensional electron gas-superconductor structure. In: Proc. 4-th Int. Semicond. Device Research Symp.; 1997. p. 163–6.
|
|
