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Author Puscasu, Irina; Boreman, Glenn D.
Title Theoretical and experimental analysis of transmission and enchanced absorption of frequency selective surfaces in the infrared Type Conference Article
Year 2001 Publication Proc. SPIE Abbreviated Journal Proc. SPIE
Volume 4293 Issue (up) Pages 185-190
Keywords optical antennas
Abstract A comparative study between theory and experiment is presented for transmission through lossy frequency selective surfaces (FSSs) on silicon in the 2 – 15 micrometer range. Important parameters controlling the resonance shape and location are identified: dipole length, spacing, impedance, and dielectric surroundings. Their separate influence is exhibited. The primary resonance mechanism of FSSs is the resonance of the individual metallic patches. There is no discernable resonance arising from a feed-coupled configuration. The real part of the element's impedance controls the minimum value of transmission, while scarcely affecting its location. Varying the imaginary part shifts the location of resonance, while only slightly changing the minimum value of transmission. With such fine-tuning, it is possible to make a good fit between theory and experiment near the dipole resonance on any sample. A fixed choice of impedance can provide a reasonable fit to all samples fabricated under the same conditions. The dielectric surroundings change the resonance wavelength of the FSS compared to its value in air. The presence of FSS on the substrate increases the absorptivity/emissivity of the surface in a resonant way. Such enhancement is shown for dipole and cross arrays at several wavelengths.
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Call Number RPLAB @ gujma @ Serial 753
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Author Pernice, W.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X.
Title High speed and high efficiency travelling wave single-photon detectors embedded in nanophotonic circuits Type Miscellaneous
Year 2012 Publication arXiv Abbreviated Journal arXiv
Volume 1108.5299 Issue (up) Pages 1-23
Keywords optical waveguides, waveguide SSPD, guantum photonics, jitter, detection efficiency
Abstract Ultrafast, high quantum efficiency single photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. High photon detection efficiency is essential for scalable measurement-based quantum computation, quantum key distribution, and loophole-free Bell experiments. However, imperfect modal matching and finite photon absorption rates have usually limited the maximum attainable detection efficiency of single photon detectors. Here we demonstrate a superconducting nanowire detector atop nanophotonic waveguides which allows us to drastically increase the absorption length for incoming photons. When operating the detectors close to the critical current we achieve high on-chip single photon detection efficiency up to 91% at telecom wavelengths, with uncertainty dictated by the variation of the waveguide photon flux. We also observe remarkably low dark count rates without significant compromise of detection efficiency. Furthermore, our detectors are fully embedded in a scalable silicon photonic circuit and provide ultrashort timing jitter of 18ps. Exploiting this high temporal resolution we demonstrate ballistic photon transport in silicon ring resonators. The direct implementation of such a detector with high quantum efficiency, high detection speed and low jitter time on chip overcomes a major barrier in integrated quantum photonics.
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Call Number Serial 845
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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.
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 Issue (up) 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 Kopp, Victor I.; Churikov, Victor M.; Zhang, Guoyin; Singer, Jonathan; Draper, Christopher W.; Chao, Norman; Neugroschl, Daniel; Genack, Azriel Z.
Title Chiral fiber gratings: perspectives and challenges for sensing applications Type Conference Article
Year 2007 Publication Proceedings of Third european workshop on optical fibre sensors Abbreviated Journal Proc. 3rd European Workshop on Opt. Fibre Sensors
Volume 6619 Issue (up) Pages 66190B-(1-8)
Keywords optical fiber gratings, chiral fiber gratings applications, chiral gratings applications, from chiralphotonics
Abstract 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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Call Number Serial 855
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Author Khosropanah, P.; Merkel, H.; Yngvesson, S.; Adam, A.; Cherednichenko, S.; Kollberg, E.
Title A distributed device model for phonon-cooled HEB mixers predicting IV characteristics, gain, noise and IF bandwidth Type Conference Article
Year 2000 Publication Proc. 11th Int. Symp. Space Terahertz Technol. Abbreviated Journal
Volume Issue (up) Pages 474-488
Keywords HEB mixer numerical model, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model
Abstract 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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Publisher Place of Publication University of Michigan, Ann Arbor, MI USA Editor
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Notes Approved no
Call Number Serial 893
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