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Author Maslennikova, Anna; Tretyakov, Ivan; Ryabchun, Sergey; Finkel, Matvey; Kaurova, Natalia; Voronov, Boris; Gol’tsman, Gregory url  openurl
  Title Gain bandwidth and noise temperature of NbN HEB mixers with simultaneous phonon and diffusion cooling Type Abstract
  Year 2010 Publication Proc. 21th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 21th Int. Symp. Space Terahertz Technol.  
  Volume (down) Issue Pages 218-219  
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  Abstract The space observatory Millimetron will be operating in the millimeter, sub-millimeter and infrared ranges using a 12-m cryogenic telescope in a single-dish mode, and as an interferometer with the space-earth and space-space baselines (the latter after the launch of the second identical space telescope). The observatory will allow performing astronomical observations with an unprecedented sensitivity (down to nJy level) in the single-dish mode, and observations with a high angular resolution in the interferometer mode. The total spectral range 20 μm – 2 cm is separated into 10 bands. HEB mixers with two cooling channels (diffusion and phonon) have been chosen to be the detectors of choice of the system covering the range from 1 THz to 6 THz as the best detectors in terahertz receivers. This type of HEB has already shown good work in the terahertz range. A gain bandwidth of 6 GHz at an LO frequency of 300 GHz and a noise temperature of 750 K at an LO frequency of 2.5 THz are the best values for HEB mixers with two cooling channels [1]. Theoretical estimations predict a bandwidth up to 12 GHz. Reaching such good result demands more systematic and thorough research. We present the results of the gain bandwidth and noise temperature measurements for superconducting hot- electron bolometer mixers with two cooling channels. These characteristics of the devices of lengths varying from 50 to 200 nm were measured for the purposes of Millimetron at frequencies of 600 GHz, 2.5 THz, and 3.8 THz. For gain bandwidth measurements we use two BWO’s operating at 600 GHz: one as the signal and the second as the LO. The noise temperature measurements were performed using a gas discharge laser as the LO and blackbodies at 77 K and 295 K as input signals. The devices studied consist of 3.5-nm-thick NbN bridges connected to thick (10 nm) high conductivity Au leads fabricated in situ. This method of fabricating devices has already proved promising by opening the diffusion cooling channel. [2] Fig. 1 shows a SEM photograph of a log-spiral antenna with an HEB at its apex. Fig. 1. Left: a SEM photograph of a log-spiral antenna with an HEB at its apex; right: a close-up of the HEB at the antenna apex. [1] S. A. Ryabchun, I. V. Tretyakov, M. I. Finkel, S. N. Maslennikov, N. S. Kaurova, V. A. Seleznev, B. M. Voronov, and G. N. Gol’tsman, NbN phonon-cooled hot-electron bolometer mixer with additional diffusion cooling, Proc. of the 20 th Int. Symp. Space. Technol., Charlottesville, Virginia, USA, April 20 – 22, 2009. 218[2] S. A. Ryabchun * , I. V. Tretyakov, M. I. Finkel, S. N. Maslennikov, N. S. Kaurova, V. A. Seleznev, B. M. Voronov and G. N. Goltsman, Fabrication and characterisation of NbN HEB mixers with in situ gold contacts, Proc. of the 19 th Int. Symp. Space. Technol., Groningen, The Netherlands, April 28-30, 2008  
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  Call Number Serial 1393  
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Author Lobanov, Y. V.; Tong, Cheuk-Yu E.; Hedden, A. S.; Blundell, R.; Gol'tsman, G. N. openurl 
  Title Microwave-assisted슠measurement슠of the슠frequency슠response슠of슠terahertz슠HEB슠mixers슠with a슠fourier슠transform슠spectrometer Type Conference Article
  Year 2010 Publication 21st International Symposium on Space Terahertz Technology Abbreviated Journal 21st ISSTT  
  Volume (down) Issue Pages 420-423  
  Keywords HEB mixer  
  Abstract We describe a novel method of operation of the HEB direct detector for use with a Fourier Transform Spectrometer. Instead of elevating the bath temperature, we have measured the RF response of waveguide HEB mixers by applying microwave radiation to select appropriate bias conditions. In our experiment, a microwave signal is injected into the HEB mixer via its IF port. By choosing an appropriate injection level, the device can be operated close to the desired operating point. Furthermore, we have shown that both thermal biasing and microwave injection can reproduce the same spectral response of the HEB mixer. However, with the use of microwave injection, there is no need to wait for the mixer to reach thermal equilibrium, so characterisation can be done in less time. Also, the liquid helium consumption for our wet cryostat is also reduced. We have demonstrated that the signalto-noise ratio of the FTS measurements can be improved with microwave injection.  
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  Call Number RPLAB @ gujma @ Serial 725  
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Author Doerr, C.R.; Zhang, C.; Winzer, P.J. openurl 
  Title Monolithic InP multi-wavelength coherent receiver Type Conference Article
  Year 2010 Publication Conference on optical fiber communication, collocated national fiber optic engineers conference Abbreviated Journal Conf. OFC/NFOEC  
  Volume (down) Issue Pages 1-3  
  Keywords InP balanced detector, waveguide grating, polarization splitter, from chiralphotonics  
  Abstract We propose and demonstrate a novel four-channel monolithic polarization-diversity dual-quadrature coherent receiver with balanced detection in InP. It uses an interleave-chirped arrayed waveguide grating that acts simultaneously as a demultiplexer, 90° hybrid, and polarization splitter.  
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  Notes Approved no  
  Call Number Serial 851  
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Author Lee, B. G.; Doany, F. E.; Assefa, S.; Green, W.; Yang, M.; Schow, C. L.; Jahnes, C. V.; Zhang, S.; Singer, J.; Kopp, V. I.; Kash, J. A.; Vlasov, Y. A. openurl 
  Title 20-μm-pitch eight-channel monolithic fiber array coupling 160 Gb/s/channel to silicon nanophotonic chip Type Conference Article
  Year 2010 Publication Conf. OFC/NFOEC Abbreviated Journal Conf. OFC/NFOEC  
  Volume (down) Issue Pages 1-3  
  Keywords spot size converters, SSC, optical waveguides, optical fiber waveguides, ultra-dense silicon waveguide arrays, silicon waveguides, waveguide arrays, from chiralphotonics  
  Abstract A multichannel tapered coupler interfacing standard 250-μm-pitch low-NA polarization-maintaining fiber arrays with ultra-dense 20-μm-pitch high-NA silicon waveguides is designed, fabricated, and tested, demonstrating coupling losses below 1 dB and injection bandwidths of 160 Gb/s/channel.  
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  Area Expedition Conference Conference on optical fiber communication, collocated national fiber optic engineers conference  
  Notes Approved no  
  Call Number Serial 852  
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Author Diana Prado Lopes Aude openurl 
  Title Modeling superconductors using surface impedance technique Type Book Whole
  Year 2010 Publication MIT Abbreviated Journal MIT  
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  Keywords homogeneous isotropic BCS superconductor complex conductivity superconductor surface impedance  
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  Notes Approved no  
  Call Number Serial 938  
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