Pyatkov, F., Khasminskaya, S., Kovalyuk, V., Hennrich, F., Kappes, M. M., Goltsman, G. N., et al. (2017). Sub-nanosecond light-pulse generation with waveguide-coupled carbon nanotube transducers. Beilstein J. Nanotechnol., 8, 38–44.
Abstract: Carbon nanotubes (CNTs) have recently been integrated into optical waveguides and operated as electrically-driven light emitters under constant electrical bias. Such devices are of interest for the conversion of fast electrical signals into optical ones within a nanophotonic circuit. Here, we demonstrate that waveguide-integrated single-walled CNTs are promising high-speed transducers for light-pulse generation in the gigahertz range. Using a scalable fabrication approach we realize hybrid CNT-based nanophotonic devices, which generate optical pulse trains in the range from 200 kHz to 2 GHz with decay times below 80 ps. Our results illustrate the potential of CNTs for hybrid optoelectronic systems and nanoscale on-chip light sources.
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Yang, Y., Fedorov, G., Shafranjuk, S. E., Klapwijk, T. M., Cooper, B. K., Lewis, R. M., et al. (2015). Electronic transport and possible superconductivity at Van Hove singularities in carbon nanotubes. Nano Lett., 15(12), 7859–7866.
Abstract: Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.
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Khasminskaya, S., Pyatkov, F., Słowik, K., Ferrari, S., Kahl, O., Kovalyuk, V., et al. (2016). Fully integrated quantum photonic circuit with an electrically driven light source. Nat. Photon., 10(11), 727–732.
Abstract: Photonic quantum technologies allow quantum phenomena to be exploited in applications such as quantum cryptography, quantum simulation and quantum computation. A key requirement for practical devices is the scalable integration of single-photon sources, detectors and linear optical elements on a common platform. Nanophotonic circuits enable the realization of complex linear optical systems, while non-classical light can be measured with waveguide-integrated detectors. However, reproducible single-photon sources with high brightness and compatibility with photonic devices remain elusive for fully integrated systems. Here, we report the observation of antibunching in the light emitted from an electrically driven carbon nanotube embedded within a photonic quantum circuit. Non-classical light generated on chip is recorded under cryogenic conditions with waveguide-integrated superconducting single-photon detectors, without requiring optical filtering. Because exclusively scalable fabrication and deposition methods are used, our results establish carbon nanotubes as promising nanoscale single-photon emitters for hybrid quantum photonic devices.
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Gayduchenko, I., Kardakova, A., Fedorov, G., Voronov, B., Finkel, M., Jiménez, D., et al. (2015). Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation. J. Appl. Phys., 118(19), 194303.
Abstract: Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors.
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Fedorov, G., Kardakova, A., Gayduchenko, I., Charayev, I., Voronov, B. M., Finkel, M., et al. (2013). Photothermoelectric response in asymmetric carbon nanotube devices exposed to sub-terahertz radiation. Appl. Phys. Lett., 103(18), 181121 (1 to 5).
Abstract: We report on the voltage response of carbon nanotube devices to sub-terahertz (THz) radiation. The devices contain carbon nanotubes (CNTs), which are over their length partially suspended and partially Van der Waals bonded to a SiO2 substrate, causing a difference in thermal contact. We observe a DC voltage upon exposure to 140 GHz radiation. Based on the observed gate voltage and power dependence, at different temperatures, we argue that the observed signal is both thermal and photovoltaic. The room temperature responsivity in the microwave to THz range exceeds that of CNT based devices reported before. Authors thank Professor P. Barbara for providing the catalyst for CNT growth and Dr. N. Chumakov and V. Rylkov for stimulating discussions. The work was supported by the RFBR (Grant No. 12-02-01291-a) and by the Ministry of Education and Science of the Russian Federation (Contract No. 14.B25.31.0007). G.F. acknowledges support of the RFBR grant 12-02-01005-a.
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