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Author Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Goltsman, G. N.; Verevkin, A. A.; Toropov, A. I.; Mauskopf, P.
Title Concentration dependence of energy relaxation time in AlGaAs/GaAs heterojunctions: direct measurements Type Journal Article
Year 2011 Publication Semicond. Sci. Technol. Abbreviated Journal Semicond. Sci. Technol.
Volume 26 Issue 2 Pages (down) 025013
Keywords AlGaAs/GaAs heterojunctions
Abstract We present measurements of the energy relaxation time, τε, of electrons in a single heterojunction in a quasi-equilibrium state using microwave time-resolved spectroscopy at 4.2 K. We find the relaxation time has a power-law dependence on the carrier density of the two-dimensional electron gas, τε∝nγs with γ = 0.40 ± 0.02 for values of the carrier density, ns, from 1.6 × 1011 to 6.6 × 1011cm−2. The results are in good agreement with predictions taking into account the scattering of the carriers by both piezoelectric and deformation potential acoustic phonons. We compare these results with indirect measurements of the energy relaxation time from energy loss measurements involving Joule heating of the electron gas.
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ISSN 0268-1242 ISBN Medium
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Call Number Serial 1215
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Author Huang, Kevin C. Y.; Jun, Young Chul; Seo, Min-Kyo; Brongersma, Mark L.
Title Power flow from a dipole emitter near an optical antenna Type Journal Article
Year 2011 Publication Optics Express Abbreviated Journal Opt. Express
Volume 19 Issue 20 Pages (down) 19084-19092
Keywords optical antennas
Abstract Current methods to calculate the emission enhancement of a quantum emitter coupled to an optical antenna of arbitrary geometry rely on analyzing the total Poynting vector power flow out of the emitter or the dyadic Green functions from full-field numerical simulations. Unfortunately, these methods do not provide information regarding the nature of the dominant energy decay pathways. We present a new approach that allows for a rigorous separation, quantification, and visualization of the emitter output power flow captured by an antenna and the subsequent reradiation power flow to the far field. Such analysis reveals unprecedented details of the emitter/antenna coupling mechanisms and thus opens up new design strategies for strongly interacting emitter/antenna systems used in sensing, active plasmonics and metamaterials, and quantum optics.
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Call Number RPLAB @ gujma @ Serial 743
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Author Miller, Aaron J.; Lita, Adriana E.; Calkins, Brice; Vayshenker, Igor; Gruber, Steven M.; Nam, Sae Woo
Title Compact cryogenic self-aligning fiber-to-detector coupling with losses below one percent Type Journal Article
Year 2011 Publication Optics Express Abbreviated Journal Opt. Express
Volume 19 Issue 10 Pages (down) 9102-9110
Keywords TES
Abstract We present a compact packaging technique for coupling light from a single-mode telecommunication fiber to cryogenic single-photon sensitive devices. Our single-photon detectors are superconducting transition-edge sensors (TESs) with a collection area only a factor of a few larger than the area of the fiber core which presents significant challenges to low-loss fiber-to-detector coupling. The coupling method presented here has low loss, cryogenic compatibility, easy and reproducible assembly and low component cost. The system efficiency of the packaged single-photon counting detectors is verified by the “triplet method” of power-source calibration along with the “multiple attenuator” method that produces a calibrated single-photon flux. These calibration techniques, when used in combination with through-wafer imaging and fiber back-reflection measurements, give us confidence that we have achieved coupling losses below 1 % for all devices packaged according to the self-alignment method presented in this paper.
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Call Number RPLAB @ gujma @ Serial 666
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Author Marsili, Francesco; Najafi, Faraz; Dauler, Eric; Bellei, Francesco; Hu, Xiaolong; Csete, Maria; Molnar, Richard J.; Berggren, Karl K.
Title Single-photon detectors based on ultranarrow superconducting nanowires Type Journal Article
Year 2011 Publication Nano Letters Abbreviated Journal Nano Lett.
Volume 11 Issue 5 Pages (down) 2048–2053
Keywords SNSPD
Abstract We report efficient single-photon detection (η = 20% at 1550 nm wavelength) with ultranarrow (20 and 30 nm wide) superconducting nanowires, which were shown to be more robust to constrictions and more responsive to 1550 nm wavelength photons than standard superconducting nanowire single-photon detectors, based on 90 nm wide nanowires. We also improved our understanding of the physics of superconducting nanowire avalanche photodetectors, which we used to increase the signal-to-noise ratio of ultranarrow-nanowire detectors by a factor of 4, thus relaxing the requirements on the read-out circuitry and making the devices suitable for a broader range of applications.
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Call Number RPLAB @ gujma @ Serial 659
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Author Barreiro, Julio T.
Title Quantum physics: Environmental effects controlled Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue Pages (down) 927–928
Keywords fromIPMRAS
Abstract An open quantum system loses its 'quantumness' when information about the state leaks into its surroundings. Researchers now show how this decoherence can be controlled between two incompatible regimes in the case of a single photon.
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Call Number RPLAB @ gujma @ Serial 817
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