| Records |
| 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 |
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Conference Article |
| Year |
2010 |
Publication |
Conf. OFC/NFOEC |
Abbreviated Journal |
Conf. OFC/NFOEC |
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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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Conference on optical fiber communication, collocated national fiber optic engineers conference |
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852 |
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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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Conference Article |
| Year |
2007 |
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Proceedings of Third european workshop on optical fibre sensors |
Abbreviated Journal |
Proc. 3rd European Workshop on Opt. Fibre Sensors |
| Volume |
6619 |
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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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Il'in, K. S.; Lindgren, M.; Currie, M. A.; Semenov, D.; Gol'tsman, G. N.; Sobolewski, Roman; Cherednichenko, S. I.; Gershenzon, E. M. |
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Picosecond hot-electron energy relaxation in NbN superconducting photodetectors |
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Journal Article |
| Year |
2000 |
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Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
76 |
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19 |
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2752-2754 |
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NbN HEB detectors, two-temperature model, IF bandwidth |
| Abstract |
We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time Ï„e–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time Ï„es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, Ï„e–ph and Ï„es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of Ï„e–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/–3) GHz if one eliminates the bolometric phonon-heating effect. |
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0003-6951 |
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856 |
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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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Conference Article |
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2000 |
Publication |
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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Kaganov, M. L.; Lifshitz, I. M.; Tanatarov, L. V. |
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Relaxation between electrons and the crystalline lattice |
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Journal Article |
| Year |
1957 |
Publication |
Sov. Phys. JETP |
Abbreviated Journal |
Sov. Phys. JETP |
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4 |
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2 |
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173-178 |
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HEB, nonlinear equations, numerical model |
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