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Author Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L.
Title A 1.8-THz quantum cascade laser operating significantly above the temperature of hw/k Type (up) Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal
Volume 7 Issue Pages 166-171
Keywords QCL, 2 mW at 155 K and 1.8 THz
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 ~planckω/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 ~1.9planckω/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 Serial 631
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Author Williams, Benjamin S.
Title Terahertz quantum-cascade lasers Type (up) Journal Article
Year 2007 Publication Nature Photonics Abbreviated Journal
Volume 1 Issue Pages 517-525
Keywords QCL review
Abstract Six years after their birth, terahertz quantum-cascade lasers can now deliver milliwatts or more of continuous-wave coherent radiation throughout the terahertz range — the spectral regime between millimetre and infrared wavelengths, which has long resisted development. This paper reviews the state-of-the-art and future prospects for these lasers, including efforts to increase their operating temperatures, deliver higher output powers and emit longer wavelengths.
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Call Number Serial 632
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Author Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim
Title Hacking commercial quantum cryptography systems by tailored bright illumination Type (up) Journal Article
Year 2010 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 4 Issue 10 Pages 686 - 689
Keywords quantum cryptography, hacking, QKD, APD
Abstract The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built of off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies.
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Call Number RPLAB @ gujma @ Serial 657
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Author Hadfield, Robert H.
Title Single-photon detectors for optical quantum information applications Type (up) Journal Article
Year 2009 Publication Nature Photonics Abbreviated Journal Nature Photonics
Volume 3 Issue Pages 696-705
Keywords SPD
Abstract The past decade has seen a dramatic increase in interest in new single-photon detector technologies. A major cause of this trend has undoubtedly been the push towards optical quantum information applications such as quantum key distribution. These new applications place extreme demands on detector performance that go beyond the capabilities of established single-photon detectors. There has been considerable effort to improve conventional photon-counting detectors and to transform new device concepts into workable technologies for optical quantum information applications. This Review aims to highlight the significant recent progress made in improving single-photon detector technologies, and the impact that these developments will have on quantum optics and quantum information science.
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Call Number RPLAB @ gujma @ Serial 678
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Author Bonifas, Andrew P.; McCreery, Richard L.
Title ‘Soft’ Au, Pt and Cu contacts for molecular junctions through surface-diffusion-mediated deposition Type (up) Journal Article
Year 2010 Publication Nature Nanotechnology Abbreviated Journal Nat. Nanotech.
Volume 5 Issue 8 Pages 612–617
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Abstract Virtually all types of molecular electronic devices depend on electronically addressing a molecule or molecular layer through the formation of a metallic contact. The introduction of molecular devices into integrated circuits will probably depend on the formation of contacts using a vapour deposition technique, but this approach frequently results in the metal atoms penetrating or damaging the molecular layer. Here, we report a method of forming 'soft' metallic contacts on molecular layers through surface-diffusion-mediated deposition, in which the metal atoms are deposited remotely and then diffuse onto the molecular layer, thus eliminating the problems of penetration and damage. Molecular junctions fabricated by this method exhibit excellent yield (typically >90%) and reproducibility, and allow examination of the effects of molecular-layer structure, thickness and contact work function.
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Call Number RPLAB @ gujma @ Serial 682
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