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Author Amzajerdian, Farzin
Title Analysis of optimum heterodyne receivers for coherent lidar applications Type Miscellaneous
Year 2002 Publication Abbreviated Journal
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Call Number Serial 505
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Author Ito, Hiroshi
Title High frequency photodiode work in Japan Type Manuscript
Year 2002 Publication Report at NTT photonics laboratories Abbreviated Journal
Volume Issue Pages 1-4
Keywords THz, terahertz communications, photodiode
Abstract The recent progress in the device performance of the uni-traveling-carrier photodiode (UTC-PD) is described. The UTC-PD utilizes only electrons as the active carriers, and this unique feature is the key to achieving excellent high-speed and high-output characteristics simultaneously. The achieved performance includes a record 3-dB bandwidth of 310 GHz, high-power photonic millimeter-wave generation with an output power of over +13 dBm at 100 GHz, high-output-voltage photoreceiver operation at bit rates of up to 80 Gbit/s, and demultiplexing operation at 200 Gbit/s using a monolithic PD-EAM optical gate.
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Call Number Serial 596
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Author Deang, Jennifer; Du, Qiang; Gunzburger, Max D.
Title Modeling and computation of random thermal fluctuations and material defects in the Ginzburg–Landau model for superconductivity Type Journal Article
Year 2002 Publication J. Comp. Phys. Abbreviated Journal
Volume 181 Issue 1 Pages 45-67
Keywords noise; superconductivity; finite element methods; fluctuations.
Abstract It is well known that thermal fluctuations and material impurities affect the motion of vortices in superconductors. These effects are modeled by variants of a time-dependent Ginzburg-Landau model containing either additive or multiplicative noise. Numerical computations are presented that illustrate the effects that noise has on the dynamics of vortex nucleation and vortex motion. For an additive noise model with relatively low variances, it is found that the vortices form a quasi-steady-state lattice in which the vortex core sizes remain roughly fixed but their positions vibrate. Two multiplicative noise models are considered. For one model having relatively long-range order, the sizes of the vortex cores vary in time and from one vortex to another. Finally, for the additive noise case, we show that as the variance of the noise tends to zero, solutions of the stochastic time-dependent Ginzburg-Landau equations converge to solutions of the corresponding equations with no noise.
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Call Number RPLAB @ gujma @ Serial 758
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Author Verevkin, A.; Zhang, J.; Slysz, W.; Sobolewski, Roman; Lipatov, A.; Okunev, O.; Chulkova, G.; Korneev, A.; Smimov, K.; Gol'tsman, G. N.
Title Spectral sensitivity and temporal resolution of NbN superconducting single-photon detectors Type Conference Article
Year 2002 Publication Proc. 13th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 13th Int. Symp. Space Terahertz Technol.
Volume Issue Pages 105-111
Keywords NbN SSPD, SNSPD
Abstract We report our studies on spectral sensitivity and time resolution of superconducting NbN thin film single-photon detectors (SPDs). Our SPDs exhibit an everimentally measured detection efficiencies (DE) from — 0.2% at 2=1550 nm up to —3% at lambda=405 nm wavelength for 10-nm film thickness devices and up to 3.5% at lambda=1550 nm for 3.5-nm film thickness devices. Spectral dependences of detection efficiency (DE) at 2=0.4 —3.0 pm range are presented. With variable optical delay setup, it is shown that NbN SPD potentially can resolve optical pulses with the repetition rate up to 10 GHz at least. The observed full width at the half maximum (FWHM) of the signal pulse is about 150-180 ps, limited by read-out electronics. The jitter of NbN SPD is measured to be —35 ps at optimum biasing.
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Call Number Serial 1528
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Author Verevkin, A. A.; Zhang, J.; Slysz, W.; Sobolewski, R.; Lipatov, A. P.; Okunev, O.; Chulkova, G.; Korneev, A.; Gol’tsman, G. N.
Title Superconducting single-photon detectors for GHz-rate free-space quantum communications Type Conference Article
Year 2002 Publication Proc. SPIE Abbreviated Journal Proc. SPIE
Volume 4821 Issue Pages 447-454
Keywords NbN SSPD, SNSPD, single-photon detector, thin-film superconductivity, quantum cryptography, ultrafast communications
Abstract We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from   5% at wavelength λ = 1550 nm up to  10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm – 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography.
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Publisher SPIE Place of Publication Editor Ricklin, J.C.; Voelz, D.G.
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Area Expedition Conference Free-Space Laser Communication and Laser Imaging II
Notes Approved no
Call Number Serial 1523
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