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- Acharya, Narendra, 1982, et al.
(författare)
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Analysis of the broad IF-band performance of MgB2 HEB mixers
- 2019
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 9:6, s. 565-571
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental study of gain and noise bandwidths in superconducting MgB2 hot-electron bolometer (HEB) terahertz mixers in a 0.1-20 GHz intermediate frequency (IF) range. At an elevated temperature and with a 90-GHz local oscillator (LO), we measure a gain bandwidth of 13-14 GHz, which is the first accurate data for ultrathin MgB2 films. The output noise spectrum has its maximum in the 100-200 K range, depending on the temperature (or the LO power) and the bias point, and its spectrum also confirms the gain bandwidth data obtained with the mixing experiment. Using both the gain and the output noise spectra, we obtain the mixer input noise temperature, which is nearly constant up to 20 GHz. Using the measured data and the HEB mixer theory, we argue that noise bandwidth in the current MgB2 HEB mixers is ∼30 GHz.
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- Cherednichenko, Serguei, 1970, et al.
(författare)
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Low kinetic inductance superconducting MgB2 nanowires with a 130-picosecond relaxation time for single-photon detection applications
- 2021
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 34:4
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Tidskriftsartikel (refereegranskat)abstract
- Properties of superconducting nanowires set the performance level for Superconducting Nanowire Single Photon Detectors (SNSPD). Reset time in commonly employed large area SNSPDs, 1-10ns, is known to be limited by the nanowire's kinetic inductance to the load impedance ratio. On the other hand, reduction of the kinetic inductance in small area (waveguide integrated) SNSPDs prevents biasing them close to the critical current due to latching into a permanent resistive state. In order to reduce the reset time in SNSPDs, superconducting nanowires with both low kinetic inductance and fast electron energy relaxation are required. In this paper, we report on a study of kinetic inductance in narrow (15-100nm) and long (up to 120m) superconducting MgB2 nanowires made from 5 nm-thick films, offering such combination of properties. Such films were grown using Hybrid Physical Chemical Vapor Deposition, resulting in a critical temperature of 32K, and a switch current density of 5107A/cm2 (at 4.8K). Using microwave reflectometry, we measured a kinetic inductance of Lk0(4.8K)=1.3-1.6 pH/ regardless of the nanowire width, which results in a magnetic field penetration depth of 90 nm. These values are very close to those in pristine MgB2. We showed that after excitations by a 50 fs pulsed laser the reset time in 35nm120m MgB2 nanowires is 130 ps, which is more than a factor of 10 shorter than in NbN nanowires of similar length-to-width ratios. Depending on the bias current, such MgB2 nanowires function as single-, double , or triple- photon detectors for both visible (= 630 nm) and infrared (= 1550 nm) photons, with a dark count rate of <10 cps. Although the apparent photon detection efficiency seems so far to be low, further technological advances (uniform nanowire width, smaller thickness, increasing the switching current closer to the pair-breaking current) may improve this figure of merit.
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