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Author Kumar, Sushil; Wang I. Chan, Chun; Hu, Qing; Reno, John L.
Title (up) A 1.8-THz quantum cascade laser operating significantly above the temperature of ω/kB Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue Pages
Keywords fromIPMRAS
Abstract Several competing technologies continue to advance the field of terahertz science; of particular importance has been the development of a terahertz semiconductor quantum cascade laser (QCL), which is arguably the only solid-state terahertz source with average optical power levels of much greater than a milliwatt. Terahertz QCLs are required to be cryogenically cooled and improvement of their temperature performance is the single most important research goal in the field. Thus far, their maximum operating temperature has been empirically limited to ~ω/kB, a largely inexplicable trend that has bred speculation that a room-temperature terahertz QCL may not be possible in materials used at present. Here, we argue that this behaviour is an indirect consequence of the resonant-tunnelling injection mechanism employed in all previously reported terahertz QCLs. We demonstrate a new scattering-assisted injection scheme to surpass this limit for a 1.8-THz QCL that operates up to ~1.9ω/kB (163 K). Peak optical power in excess of 2 mW was detected from the laser at 155 K. This development should make QCL technology attractive for applications below 2 THz, and initiate new design strategies for realizing a room-temperature terahertz semiconductor laser.
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Call Number RPLAB @ gujma @ Serial 836
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Author Tassin, Philippe; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas M.
Title (up) A comparison of graphene, superconductors and metals as conductors for metamaterials and plasmonics Type Journal Article
Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 6 Issue 4 Pages 259-264
Keywords fromIPMRAS
Abstract Recent advancements in metamaterials and plasmonics have promised a number of exciting applications, in particular at terahertz and optical frequencies. Unfortunately, the noble metals used in these photonic structures are not particularly good conductors at high frequencies, resulting in significant dissipative loss. Here, we address the question of what is a good conductor for metamaterials and plasmonics. For resonant metamaterials, we develop a figure-of-merit for conductors that allows for a straightforward classification of conducting materials according to the resulting dissipative loss in the metamaterial. Application of our method predicts that graphene and high-Tc superconductors are not viable alternatives for metals in metamaterials. We also provide an overview of a number of transition metals, alkali metals and transparent conducting oxides. For plasmonic systems, we predict that graphene and high-Tc superconductors cannot outperform gold as a platform for surface plasmon polaritons, because graphene has a smaller propagation length-to-wavelength ratio.
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Call Number RPLAB @ gujma @ Serial 790
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Author Zhu, J.; Christensen, J.; Jung, J.; Martin-Moreno, L.; Yin, X.; Fok, L.; Zhang, X.; Garcia-Vidal, F. J.
Title (up) A holey-structured metamaterial for acoustic deep-subwavelength imaging Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 1 Pages 52-55
Keywords fromIPMRAS
Abstract For classical waves such as light or sound, diffraction sets a natural limit on how finely the details of an object can be recorded on its image. Recently, various optical superlenses based on the metamaterials concept have shown the possibility of overcoming the diffraction limit. Similar two-dimensional (2D) acoustic hyperlens designs have also been explored. Here we demonstrate a 3D holey-structured metamaterial that achieves acoustic imaging down to a feature size of λ/50. The evanescent field components of a subwavelength object are efficiently transmitted through the structure as a result of their strong coupling with Fabry-Pérot resonances inside the holey plate. This capability of acoustic imaging at a very deep-subwavelength scale may open the door for a broad range of applications, including medical ultrasonography, underwater sonar and ultrasonic non-destructive evaluation.
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Call Number RPLAB @ gujma @ Serial 809
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Author Hannay, Timo
Title (up) A new kind of science? Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue Pages 742
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Call Number RPLAB @ gujma @ Serial 818
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Author Fuchs, G. D.; Burkard, G.; Klimov, P. V.; Awschalom, D. D.
Title (up) A quantum memory intrinsic to single nitrogen–vacancy centres in diamond Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 10 Pages 789-793
Keywords fromIPMRAS
Abstract A quantum memory, composed of a long-lived qubit coupled to each processing qubit, is important to building a scalable platform for quantum information science. These two qubits should be connected by a fast and high-fidelity operation to store and retrieve coherent quantum states. Here, we demonstrate a room-temperature quantum memory based on the spin of the nitrogen nucleus intrinsic to each nitrogen–vacancy (NV) centre in diamond. We perform coherent storage of a single NV centre electronic spin in a single nitrogen nuclear spin using Landau–Zener transitions across a hyperfine-mediated avoided level crossing. By working outside the asymptotic regime, we demonstrate coherent state transfer in as little as 120 ns with total storage fidelity of 88±6%. This work demonstrates the use of a quantum memory that is compatible with scaling as the nitrogen nucleus is deterministically present in each NV centre defect.
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Call Number RPLAB @ gujma @ Serial 823
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