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Fedorov, G., Kardakova, A., Gayduchenko, I., Voronov, B. M., Finkel, M., Klapwijk, T. M., et al. (2014). Photothermoelectric response in asymmetric carbon nanotube devices exposed to sub-THz radiation. In Proc. 25th Int. Symp. Space Terahertz Technol. (71).
Abstract: This work reports on the voltage response of asymmetric carbon nanotube devices to sub-THz radiation at the frequency of 140 GHz. The devices contain CNT’s, which are over their length partially suspended and partially Van der Waals bonded to a SiO 2 substrate, causing a difference in thermal contact. Different heat sinking of CNTs by source and drain gives rise to temperature gradient and consequent thermoelectric power (TEP) as such a device is exposed to the sub-THz radiation. Sign of the DC signal, its power and gate voltage dependence observed at room temperature are consistent with this scenario. At liquid helium temperature the observed response is more complex. DC voltage signal of an opposite sign is observed in a narrow range of gate voltages at low temperatures and under low radiation power. We argue that this may indicate a true photovoltaic response from small gap (less than 10meV) CNT’s, an effect never reported before. While it is not clear if the observed effects can be used to develop efficient THz detectors we note that the responsivity of our devices exceeds that of CNT based devices in microwave or THz range reported before at room temperature. Besides at 4.2 K notable increase of the sample conductance (at least four-fold) is observed. Our recent results with asymmetric carbon nanotube devices response to THz radiation (2.5 THz) will also be presented.
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Tretyakov, I., Kaurova, N., Voronov, B. M., & Goltsman, G. N. (2018). About effect of the temperature operating conditions on the noise temperature and noise bandwidth of the terahertz range NbN hot-electron bolometers. In Proc. 29th Int. Symp. Space Terahertz Technol. (113).
Abstract: Results of an experimental study of the noise temperature (Tn) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (Tb) and NbN bridge length are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (Tc) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature Tb close to Tc was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at Tb ≪ Tc for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.
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Vorobyov, V. V., Kazakov, A. Y., Soshenko, V. V., Korneev, A. A., Shalaginov, M. Y., Bolshedvorskii, S. V., et al. (2017). Superconducting detector for visible and near-infrared quantum emitters [Invited]. Opt. Mater. Express, 7(2), 513–526.
Abstract: Further development of quantum emitter based communication and sensing applications intrinsically depends on the availability of robust single-photon detectors. Here, we demonstrate a new generation of superconducting single-photon detectors specifically optimized for the 500–1100 nm wavelength range, which overlaps with the emission spectrum of many interesting solid-state atom-like systems, such as nitrogen-vacancy and silicon-vacancy centers in diamond. The fabricated detectors have a wide dynamic range (up to 350 million counts per second), low dark count rate (down to 0.1 counts per second), excellent jitter (62 ps), and the possibility of on-chip integration with a quantum emitter. In addition to performance characterization, we tested the detectors in real experimental conditions involving nanodiamond nitrogen-vacancy emitters enhanced by a hyperbolic metamaterial.
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