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Kopp, Victor I.; Churikov, Victor M.; Zhang, Guoyin; Singer, Jonathan; Draper, Christopher W.; Chao, Norman; Neugroschl, Daniel; Genack, Azriel Z. |
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Chiral fiber gratings: perspectives and challenges for sensing applications |
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2007 |
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Proceedings of Third european workshop on optical fibre sensors |
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Proc. 3rd European Workshop on Opt. Fibre Sensors |
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6619 |
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66190B-(1-8) |
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optical fiber gratings, chiral fiber gratings applications, chiral gratings applications, from chiralphotonics |
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Chiral fiber gratings are produced in a microforming process in which optical fibers with noncircular or nonconcentric cores are twisted as they pass though a miniature oven. Periodic glass structures as stable as the glass material itself are produced with helical pitch that ranges from under a micron to hundreds of microns. The geometry of the fiber cross section determines the symmetry of the resulting structure which in turn determines its polarization selectivity. Single helix structures are polarization insensitive while double helix gratings interact only with a single optical polarization. Both single and double helix gratings may act as a fiber long period grating, coupling the core and cladding modes. The coupling is manifested in a series of narrow dips in the transmission spectrum. The dip position is sensitive to fiber elongation, twist and temperature, and to the refractive index of the surrounding medium. The suitability of chiral gratings for sensing pressure, temperature and liquid levels is investigated. Polarization insensitive single helix silica glass gratings display excellent stability up to temperatures of 6000C, while a pressure sensor with dynamic range of nearly 40 dB is demonstrated in polarization selective double helix gratings. |
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Khosropanah, P.; Merkel, H.; Yngvesson, S.; Adam, A.; Cherednichenko, S.; Kollberg, E. |
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A distributed device model for phonon-cooled HEB mixers predicting IV characteristics, gain, noise and IF bandwidth |
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2000 |
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Proc. 11th Int. Symp. Space Terahertz Technol. |
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474-488 |
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HEB mixer numerical model, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model |
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A distributed model for phonon-cooled superconductor hot electron bolometer (HEB) mixers is given, which is based on solving the one-dimensional heat balance equation for the electron temperature profile along the superconductor strip. In this model it is assumed that the LO power is absorbed uniformly along the bridge but the DC power absorption depends on the local resistivity and is thus not uniform. The electron temperature dependence of the resistivity is assumed to be continuous and has a Fermi form. These assumptions are used in setting up the non-linear heat balance equation, which is solved numerically for the electron temperature profile along the bolometer strip. Based on this profile the resistance of the device and the IV curves are calculated. The IV curves are in excellent agreement with measurement results. Using a small signal model the conversion gain of the mixer is obtained. The expressions for Johnson noise and thermal fluctuation noise are derived. The calculated results are in close agreement with measurements, provided that one of the parameters used is adjusted. |
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University of Michigan, Ann Arbor, MI USA |
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893 |
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Ynvesson, K. Sigfrid; Kollberg, Erik L. |
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Optimum receiver noise temperature for NbN HEB mixers according to standard model |
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1999 |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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566-582 |
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HEB mixer model, standard model, electro-thermal feedback, self-heating parameter, heating efficiency |
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Benford, Dominic; Moseley, Harvey; Zmuidzinas, Jonas |
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Direct detectors for the Einstein inflation probe |
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2009 |
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J. Phys.: Conf. Ser. |
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J. Phys.: Conf. Ser. |
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155 |
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1 |
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012001 (1 to 49) |
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KID, MKID, CMB |
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Here we review the principles of operation, history, present status, and future prospects for the primary candidate detectors for Cosmic Microwave Background (CMB) polarization studies. The three detector types we will discuss are semiconductor-based bolometers, superconducting transition edge sensor (TES) bolometer, and Microwave Kinetic Inductance Detectors (MKIDs). All of these detector types can provide the sensitivity to permit background-limited measurements of the CMB, but the ultimate selection of detectors will be largely determined by the ease of production and reliability of large arrays of such detectors. This paper describes the present state of development of these detectors, efforts to integrate them into large arrays, and the detector system developments necessary to enable a space CMB polarization mission. |
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Recommended by Klapwijk |
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913 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Golts'man, G.; Gershenzon, E.; Voronov B. |
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Superconductive NbN hot-electron bolometric mixer performance at 250 GHz |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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331-336 |
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NbN HEB mixers |
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Thin film NbN (<40 A) strips are used as waveguide mixer elements. The electron cooling mechanism for the geometry is the electron-phonon interaction. We report a receiver noise temperature of 750 K at 244 GHz, with / IF = 1.5 GHz, Af= 500 MHz, and Tphysical = 4 K. The instantaneous bandwidth for this mixer is 1.6 GHz. The local oscillator (LO) power is 0.5 1.tW with 3 dB-uncertainty. The mixer is linear to 1 dB up to an input power level 6 dB below the LO power. We report the first detection of a molecular line emission using this class of mixer, and that the receiver noise temperature determined from Y-factor measurements reflects the true heterodyne sensitivity. |
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