24,091 research outputs found

    Photonic millimeter-wave frequency multiplication based on cascaded four-wave mixing and polarization pulling

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    This paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.37.005055. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] A technique for the frequency multiplication of microwave signals based on the combination of two optical nonlinear phenomena in a single nonlinear fiber is investigated. Multiple four-wave mixing is used to generate harmonics on an externally modulated optical carrier while polarization pulling through stimulated Brillouin scattering is used to filter the desired harmonics. Microwave signals in the 60 GHz region are generated showing harmonic frequency multiplication factors of up to 25 with a suppression of undesired harmonics better than 20 dB. © 2012 Optical Society of America.This research was supported in part by the Spanish Ministerio de Economia y Competitividad through TEC2009-08078 and TEC2012-35797 projects.Vidal Rodriguez, B. (2012). Photonic millimeter-wave frequency multiplication based on cascaded four-wave mixing and polarization pulling. Optics Letters. 37(24):25478-25488. https://doi.org/10.1364/OL.37.005055S25478254883724Kawanishi, T., Oikawa, S., Yoshiara, K., Sakamoto, T., Shinada, S., & Izutsu, M. (2005). Low noise photonic Millimeter-wave generation using an integrated reciprocating optical Modulator. IEEE Photonics Technology Letters, 17(3), 669-671. doi:10.1109/lpt.2004.842377Li, W., & Yao, J. (2010). Investigation of Photonically Assisted Microwave Frequency Multiplication Based on External Modulation. IEEE Transactions on Microwave Theory and Techniques, 58(11), 3259-3268. doi:10.1109/tmtt.2010.2075671Vidal, B., Huggard, P. G., Ellison, B. N., & Gomes, N. J. (2010). Optoelectronic generation of W-band millimetre-wave signals using Brillouin amplification. Electronics Letters, 46(21), 1449. doi:10.1049/el.2010.2310Wiberg, A., Perez-Millan, P., Andres, M. V., & Hedekvist, P. O. (2006). Microwave-photonic frequency multiplication utilizing optical four-wave mixing and fiber Bragg gratings. Journal of Lightwave Technology, 24(1), 329-334. doi:10.1109/jlt.2005.860164Wang, Q., Rideout, H., Zeng, F., & Yao, J. (2006). Millimeter-Wave Frequency Tripling Based on Four-Wave Mixing in a Semiconductor Optical Amplifier. IEEE Photonics Technology Letters, 18(23), 2460-2462. doi:10.1109/lpt.2006.886826Li, Y., Naderi, N. A., Kovanis, V., & Lester, L. F. (2010). Enhancing the 3-dB Bandwidth via the Gain-Lever Effect in Quantum-Dot Lasers. IEEE Photonics Journal, 2(3), 321-329. doi:10.1109/jphot.2010.2046481McKinstrie, C. J., & Raymer, M. G. (2006). Four-wave-mixing cascades near the zero-dispersion frequency. Optics Express, 14(21), 9600. doi:10.1364/oe.14.009600Cerqueira Sodre, A., Chavez Boggio, J. M., Rieznik, A. A., Hernandez-Figueroa, H. E., Fragnito, H. L., & Knight, J. C. (2008). Highly efficient generation of broadband cascaded four-wave mixing products. Optics Express, 16(4), 2816. doi:10.1364/oe.16.002816Wise, A., Tur, M., & Zadok, A. (2011). Sharp tunable optical filters based on the polarization attributes of stimulated Brillouin scattering. Optics Express, 19(22), 21945. doi:10.1364/oe.19.021945Hansryd, J., Andrekson, P. A., Westlund, M., Jie Li, & Hedekvist, P.-O. (2002). Fiber-based optical parametric amplifiers and their applications. IEEE Journal of Selected Topics in Quantum Electronics, 8(3), 506-520. doi:10.1109/jstqe.2002.101635

    Anomalous precursor diamagnetism at low reduced magnetic fields and the role of Tc inhomogeneities in the superconductors Pb55In45 and underdoped La1.9Sr0.1CuO4

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    The magnetic field dependence of the magnetization was measured above the superconducting transition in a high-Tc underdoped cuprate La1.9Sr0.1CuO4 and in a low-Tc alloy (Pb55In45). Near the superconducting transition [typically for (T-Tc)/Tc<0.05] and under low applied magnetic field amplitudes [typically for H/Hc2(0)<0.01, where Hc2(0) is the corresponding upper critical field extrapolated to T=0 K] the magnetization of both samples presents a diamagnetic contribution much larger than the one predicted by the Gaussian Ginzburg-Landau (GGL) approach for superconducting fluctuations. These anomalies have been already observed in cuprate compounds by various groups and attributed to intrinsic effects associated with the own nature of these high-Tc superconductors. However, we will see here that our results in both high and low-Tc superconductors may be explained quantitatively, and consistently with the GGL behavior observed at higher fields, by just taking into account the presence in the samples of an uniform distribution of Tc inhomogeneities. These Tc inhomogeneities, which may be in turn associated with stoichiometric inhomogeneities, were estimated from independent measurements of the temperature dependence of the field-cooled magnetic susceptibility under low applied magnetic fields.Comment: 25 pages, including 6 figures and 1 table. Typos corrected. Compacte

    Nonperturbative renormalization group approach to the Ising model: a derivative expansion at order 4\partial^4

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    On the example of the three-dimensional Ising model, we show that nonperturbative renormalization group equations allow one to obtain very accurate critical exponents. Implementing the order 4\partial^4 of the derivative expansion leads to ν=0.632\nu=0.632 and to an anomalous dimension η=0.033\eta=0.033 which is significantly improved compared with lower orders calculations.Comment: 4 pages, 3 figure

    Aharonov-Bohm cages in the GaAlAs/GaAs system

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    Aharonov-Bohm oscillations have been observed in a lattice formed by a two dimensional rhombus tiling. This observation is in good agreement with a recent theoretical calculation of the energy spectrum of this so-called T3 lattice. We have investigated the low temperature magnetotransport of the T3 lattice realized in the GaAlAs/GaAs system. Using an additional electrostatic gate, we have studied the influence of the channel number on the oscillations amplitude. Finally, the role of the disorder on the strength of the localization is theoretically discussed.Comment: 6 pages, 11 EPS figure

    An evaluation of superminicomputers for thermal analysis

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    The feasibility and cost effectiveness of solving thermal analysis problems on superminicomputers is demonstrated. Conventional thermal analysis and the changing computer environment, computer hardware and software used, six thermal analysis test problems, performance of superminicomputers (CPU time, accuracy, turnaround, and cost) and comparison with large computers are considered. Although the CPU times for superminicomputers were 15 to 30 times greater than the fastest mainframe computer, the minimum cost to obtain the solutions on superminicomputers was from 11 percent to 59 percent of the cost of mainframe solutions. The turnaround (elapsed) time is highly dependent on the computer load, but for large problems, superminicomputers produced results in less elapsed time than a typically loaded mainframe computer

    An evaluation of superminicomputers for thermal analysis

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    The use of superminicomputers for solving a series of increasingly complex thermal analysis problems is investigated. The approach involved (1) installation and verification of the SPAR thermal analyzer software on superminicomputers at Langley Research Center and Goddard Space Flight Center, (2) solution of six increasingly complex thermal problems on this equipment, and (3) comparison of solution (accuracy, CPU time, turnaround time, and cost) with solutions on large mainframe computers
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