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Sekine, Norihiko; Hosako, Iwao |
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Intensity modulation of terahertz quantum cascade lasers under external light injection |
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Journal Article |
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2009 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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95 |
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201106(1-3) |
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QCL modulation, THz, terahertz |
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We investigated the light-current characteristics of terahertz (THz) quantum cascade lasers under external light injection, which excites interband transitions in the active materials. It was found that the amount of reduction in the THz power was constant for all injection currents above threshold, and the dependence of the reduction amount on the wavelength of the external light was observed to show a resonancelike feature. The dominant intensity modulation mechanism was found to be the loss change caused by interband transitions in the active region. Further, the effective coupling efficiency plays an important role in the intensity modulation. |
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630 |
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Xiaolong Hu; Holzwarth, C.W.; Masciarelli, D.; Dauler, E.A.; Berggren, K.K. |
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Efficiently coupling light to superconducting nanowire single-photon detectors |
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Journal Article |
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2009 |
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IEEE Trans. Appl. Supercond. |
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19 |
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3 |
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336-340 |
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optical antennas; SNSPD |
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We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for the fiber coupling, the absorptance of the NbN nanowire for TE-like-polarized photons can reach 76% including coupling efficiency at the wavelength of 1550 nm by adding a silicon nitride waveguide and an inverse-taper coupler. |
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RPLAB @ gujma @ |
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647 |
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Kern, Pierre; Le Coärer, Etienne; Benech, Pierre |
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On-chip spectro-detection for fully integrated coherent beam combiners |
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Journal Article |
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2009 |
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Optics Express |
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Opt.Express |
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17 |
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3 |
Pages |
1976-1987 |
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This paper presents how photonics associated with new arising detection technologies is able to provide fully integrated instrument for coherent beam combination applied to astrophysical interferometry. The feasibility and operation of on-chip coherent beam combiners has been already demonstrated using various interferometric combination schemes. More recently we proposed a new detection principle aimed at directly sampling and extracting the spectral information of an input signal together with its flux level measurement. The so-called SWIFTS demonstrated concept that stands for Stationary-Wave Integrated Fourier Transform Spectrometer, provides full spectral and spatial information recorded simultaneously thanks to a motionless detecting device. Due to some newly available detection principles considered for the implementation of the SWIFTS concept, some technologies can even provide photo-counting operation that brought a significant extension of the interferometry domain of investigation in astrophysics. The proposed concept is applicable to most of the interferometric instrumental modes including fringe tracking, fast and sensitive detection, Fourier spectral reconstruction and also to manage a large number of incoming beams. The paper presents three practical implementations, two dealing with pair-wise integrated optics beam combinations and the third one with an all-in-one 8 beam combination. In all cases the principles turned into a pair wise baseline coding after proper data processing. |
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RPLAB @ gujma @ |
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650 |
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Author |
Zhizhon, Yan; Majedi, Hamed A. |
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Optoelectronic mixing in the NbN superconducting nanowire single photon detectors |
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Conference Article |
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2009 |
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Proc. SPIE |
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Proc. SPIE |
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3786 |
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9 |
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Optoelectronic devices, microwave superconductivity, nonlinearity, single photon detector, superconductivity, nanowire, optical mixing, microwave mixers, amplitude modulation, intensity modulation. |
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In this paper, we present our experimental results on the electrically pumped optoelectronic mixing effect exhibited in a niobium nitride (NbN) superconducting nanowire. The experimental setup in order to test the mixer has been reported in detail. This superconductive nanowire optoelectronic mixer demonstrates photodetection and mixing in an integrated manner. We have explored both effects under a great variety of external conditions, such as temperature and bias current, in order to seek potential ways toward quantum optoelectronic detection and mixing by such nanowire device. |
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RPLAB @ gujma @ |
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651 |
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Author |
Scheel, Stefan |
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Title |
Single-photon sources–an introduction |
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2009 |
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J. Modern Opt. |
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56 |
Issue |
2-3 |
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141-160 |
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LOQC; quantum cryptography; QKD |
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This review surveys the physical principles and recent developments in manufacturing single-photon sources. Special emphasis is placed on important potential applications such as linear optical quantum computing (LOQC), quantum key distribution (QKD) and quantum metrology that drive the development of these sources of single photons. We discuss the quantum-mechanical properties of light prepared in a quantum state of definite photon number and compare it with coherent light that shows a Poissonian distribution of photon numbers. We examine how the single-photon fidelity directly influences the ability to transmit secure quantum bits over a predefined distance. The theoretical description of modified spontaneous decay, the main principle behind single-photon generation, provides the background for many experimental implementations such as those using microresonators or pillar microcavities. The main alternative way to generate single photons using postselection of entangled photon pairs from parametric down-conversion, will be discussed. We concentrate on describing the underlying physical principles and we will point out limitations and open problems associated with single-photon production. |
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RPLAB @ gujma @ |
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669 |
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