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Hajenius, M., Baselmans, J. J. A., Gao, J. R., Klapwijk, T. M., de Korte, P. A. J., Voronov, B., et al. (2004). Low noise NbN superconducting hot electron bolometer mixers at 1.9 and 2.5 THz. Supercond. Sci. Technol., 17(5), S224–S228.
Abstract: NbN phonon-cooled hot electron bolometer mixers (HEBs) have been realized with negligible contact resistance between the bolometer itself and the contact structure. Using a combination of in situ cleaning of the NbN film and the use of an additional superconducting interlayer of a 10 nm NbTiN layer between the Au of the contact structure and the NbN film superior noise temperatures have been obtained as low as 950 K at 2.5 THz and 750 K at 1.9 THz. Here we address in detail the DC characterization of these devices, the interface transparencies between the bolometers and the contacts and the consequences of these factors on the mixer performance.
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Finkel, M. I., Maslennikov, S. N., & Gol'tsman, G. N. (2007). The concept of the receiving complex for the “Millimetron” space radio telescope. Radiophys. Quant. Electron., 50(10-11), 837–846.
Abstract: We consider the current status of research in the development of a submillimeter and far-infrared receiving instrument and propose promising solutions for the receivers of the spaceborne telescope “Millimetron,” which allow one to realize comprehensively the opportunities given by this international project administrated by the Astrospace Center of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences.
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Ryabchun, S. A., Tretyakov, I. V., Finkel, M. I., Maslennikov, S. N., Kaurova, N. S., Seleznev, V. A., et al. (2008). Fabrication and characterisation of NbN HEB mixers with in situ gold contacts. In Proc. 19th Int. Symp. Space Terahertz Technol. (pp. 62–67). Groningen, Netherlands.
Abstract: We present our recent results of the fabrication and testing of NbN hot-electron bolometer mixers with in situ gold contacts. An intermediate frequency bandwidth of about 6 GHz has been measured for the mixers made of a 3.5-nm NbN film on a plane Si substrate with in situ gold contacts, compared to 3.5 GHz for devices made of the same film with ex situ gold contacts. The increase in the intermediate frequency bandwidth is attributed to additional diffusion cooling through the improved contacts, which is further supported by the its dependence on the bridge length: intermediate frequency bandwidths of 3.5 GHz and 6 GHz have been measured for devices with lengths of 0.35 μm and 0.16 μm respectively at a local oscillator frequency of 300 GHz near the superconducting transition. At a local oscillator frequency of 2.5 THz the receiver has offered a DSB noise temperature of 950 K. When compared to the previous result of 1300 K obtained at the same local oscillator frequency for devices fabricated with an ex situ route, such a low value of the noise temperature may also be attributed to the improved gold contacts.
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Yagoubov, P., van de Stadt, H., Hoogeveen, R., Koshelets, V., Birk, M., & Murk, A. (2005). OPTICAL DESIGN OF SUB-MILLIMETER SPECTROMETER FOR LIMB SOUNDER. International Symposium on Space Terahertz Technology, .
Abstract: TELIS (Terahertz and submm Limb Sounder) is a cooperation between DLR (Institute for Remote Sensing Technology, Germany), RAL (Rutherford Appleton Laboratories, UK) and SRON (National Institute for Space Research, the Netherlands), to build a three-channel balloon-borne heterodyne spectrometer for atmospheric research. The three receivers will operate simultaneously at 500 GHz (channel developed by RAL), at 550-650 GHz (SRON in collaboration with IREE), and at 1.8 THz (DLR). The balloon platform on which TELIS will fly also contains a Fourier transform spectrometer: MIPAS-B developed by the IMK (Institute of Meteorology and Climate research of the University of Karlsruhe, Germany). MIPAS-B will simultaneously measure within the range 680 to 2400 cm-1. The combination of the TELIS and MIPAS instruments will provide an unprecedented wealth of scientific data and will also be used to validate other instruments and atmospheric chemistry models. In this paper we present the optical design of TELIS with an emphasis on the 550-650 GHz channel. The main design goal was to generate a high efficiency antenna beam over the full frequency range, with low side lobes and close to diffraction limited angular resolution in the vertical direction at the sky. All these requirements had to be achieved within a small volume and low mass. Design and validation of the optics, as well as estimation of optical components tolerances, was done using commercial software packages ZEMAX and GRASP.
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Semenov, A. D., Gol'tsman, G. N., & Sobolewski, R. (2002). Hot-electron effect in superconductors and its applications for radiation sensors. Supercond. Sci. Technol., 15(4), R1–R16.
Abstract: The paper reviews the main aspects of nonequilibrium hot-electron phenomena in superconductors and various theoretical models developed to describe the hot-electron effect. We discuss implementation of the hot-electron avalanche mechanism in superconducting radiation sensors and present the most successful practical devices, such as terahertz mixers and direct intensity detectors, for far-infrared radiation. Our presentation also includes the novel approach to hot-electron quantum detection implemented in superconducting x-ray to optical photon counters.
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