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Mohan N, Minaeva O, Goltsman GN, Saleh MF, Nasr MB, Sergienko AV, et al. Ultrabroadband coherence-domain imaging using parametric downconversion and superconducting single-photon detectors at 1064 nm. Appl Opt. 2009;48(20):4009–4017.
Abstract: Coherence-domain imaging systems can be operated in a single-photon-counting mode, offering low detector noise; this in turn leads to increased sensitivity for weak light sources and weakly reflecting samples. We have demonstrated that excellent axial resolution can be obtained in a photon-counting coherence-domain imaging (CDI) system that uses light generated via spontaneous parametric downconversion (SPDC) in a chirped periodically poled stoichiometric lithium tantalate (chirped-PPSLT) structure, in conjunction with a niobium nitride superconducting single-photon detector (SSPD). The bandwidth of the light generated via SPDC, as well as the bandwidth over which the SSPD is sensitive, can extend over a wavelength region that stretches from 700 to 1500 nm. This ultrabroad wavelength band offers a near-ideal combination of deep penetration and ultrahigh axial resolution for the imaging of biological tissue. The generation of SPDC light of adjustable bandwidth in the vicinity of 1064 nm, via the use of chirped-PPSLT structures, had not been previously achieved. To demonstrate the usefulness of this technique, we construct images for a hierarchy of samples of increasing complexity: a mirror, a nitrocellulose membrane, and a biological sample comprising onion-skin cells.
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Sych D, Shcherbatenko M, Elezov M, Goltsman GN. Towards the improvement of the heterodyne receiver sensitivity beyond the quantum noise limit. In: Proc. 29th Int. Symp. Space Terahertz Technol.; 2018. p. 245–7.
Abstract: Noise reduction in heterodyne receivers of the terahertz range is an important issue for astronomical applications. Quantum fluctuations, also known as shot noise, prohibit errorless measurements of the amplitude of electro-magnetic waves, and introduce the so-called standard quantum limit (SQL) on the minimum error of the heterodyne measurements. Nowadays, the sensitivity of modern heterodyne receivers approaches the SQL, and the growing demand for the improvement of measurement precision stimulates a number of both theoretical and experimental efforts to design novel measurement techniques aimed at overcoming the SQL. Here we demonstrate the first steps towards the practical implementation of a sub-SQL quantum receiver. As the principal resources, it requires a highly efficient single-photon counting detector and an interferometer-based scheme for mixing the signal with a low-power local oscillator. We describe the idea of such receiver and its main components.
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Goltsman GN, Vachtomin YB, Antipov SV, Finkel MI, Maslennikov SN, Polyakov SL, et al. Low-noise NbN phonon-cooled hot-electron bolometer mixers for terahertz heterodyne receivers. In: Proc. 9-th WMSCI. Vol 9. International Institute of Informatics and Systemics; 2005. p. 154–9.
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Seliverstov SV, Rusova AA, Kaurova NS, Voronov BM, Goltsman GN. AC-biased superconducting NbN hot-electron bolometer for frequency-domain multiplexing. In: Proc. 28th Int. Symp. Space Terahertz Technol.; 2017. p. 120–2.
Abstract: We present the results of characterization of fast and sensitive superconducting antenna-coupled THz direct detector based on NbN hot-electron bolometer (HEB) with AC-bias. We discuss the possibility of implementation of the AC-bias for design the readout system from the multi-element arrays of HEBs using standard technique of frequency-domain multiplexing. We demonstrate experimentally that this approach does not lead to significant deterioration of the HEB sensitivity compared with the value obtained for the same detector with DC- bias. Results of a numerical calculations of the HEB responsivity at AC-bias are in a good agreement with the experiment.
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Goltsman GN. Development and applications of terahertz hot electron bolometers [abstract]. In: 1st Moscow Int. Conf. on Submillimeter and Millimeter Astronomy: Objectives and Instruments.; 2021.
Abstract: The development of techniques and technologies for the deposition of ultrathin superconducting films, the creation of superconducting structures on a nanometer scale is the basis of significant progress in the field of superconducting receiving systems. Ultrathin NbN films are the basis for a wide range of record-breaking hot electron devices: direct and heterodyne terahertz detectors. Terahertz receivers are especially in demand in high-resolution spectroscopy for astronomical, atmospheric, and medical research. HEB receivers are widely used in terahertz radio astronomy. For example, the Dutch SRON Institute is preparing a project for the GUSTO hot air balloon telescope with a HEB mixer array at 1.4 THz and 1.9 THz. A 5-meter Chinese terahertz telescope DATE5 with HEB mixers at 1.4 THz is installed at the South Pole. The Stratospheric Observatory (SOFIA) uses HEB mixer matrices in the GREAT instrument operating in the 1.2 – 4.7 THz range. It is planned to implement the international project Origins Space Telescope (OST) in the far infrared region based on HEB receivers. The Japanese project Smiles-2 will allow measurements at 1.8 THz in the upper layers of the stratosphere and mesosphere. The development of the Millimetron space observatory continues in Russia.
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