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Li, Chao-Te; Chen, Tse-Jun; Ni, Tong-Liang; Lu, Wei-Chun; Chiu, Chuang-Ping; Chen, Chong-Wen; Chang, Yung-Chin; Wang, Ming-Jye Shi, Sheng-Cai |
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Development of SIS mixers for SMA 400-520 GHz band |
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2009 |
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Proc. 20th Int. Symp. Space Terahertz Technol. |
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24-30 |
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SIS mixer, noise temperature, SMA |
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SIS junction mixers were developed for SMA 400-520 GHz band. The results show receiver noise temperature around 100 K across the band, with noise contribution from RF loss and IF estimated to be around 50 K and 20K, respectively. Two schemes were used to tune out junction's parasitic capacitance. When a parallel inductor is employed, the input impedance is close to Rn, which facilitates impedance matching between the junction and the waveguide probe. Waveguide probes were designed to achieve a low feed-point impedance to match to the junction resistance. Optimum embedding impedances for lower receiver noise temperature were investigated. Performances of two schemes and composition of receiver noise were also discussed. |
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617 |
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Jackson, B. D.; Hesper, R.; Adema, J.; Barkhof, J.; Baryshev, A. M.; Zijlstra, T.; Zhu, S.; Klapwijk, T. M. |
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Series production of state-of-the-art 602-720 GHz SIS receivers for band 9 of ALMA |
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2009 |
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Proc. 20th Int. Symp. Space Terahertz Technol. |
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7-11 |
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SIS mixer, noise temperature, ALMA, band 9 |
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The Atacama Large Millimeter/Sub-millimeter Array (ALMA) requires the development and production of 73 state-of-the-art receivers for the 602-720 GHz range – the ALMA Band 9 cartridges. Development and pre-production of the first 8 cartridges was completed between 2003 and 2008, resulting in a cartridge design that meets the project's challenging requirements. The cartridge design remains essentially unchanged for production, while the production and test processes developed during pre-production have been fine-tuned to address the biggest new challenge for this phase – ramping up production to a rate of 2 cartridges per month over 2009-2012. |
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618 |
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Risacher, C.; Meledin, D.; Belitsky, V.; Bergman, P. |
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First 1.3 THz observations at the APEX telescope |
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2009 |
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Proc. 20th Int. Symp. Space Terahertz Technol. |
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54-61 |
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balanced HEB mixer noise temperature APEX telescope stability Allan variance aperture efficiency |
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The Atacama Pathfinder EXperiment (APEX) 12m telescope is operating on the Llano Chajnantor, Chile, since 2003 and a set of state of the art sub-millimeter receivers have been installed for frequencies spanning from 150 GHz to 1500 GHz. In 2008, a balanced 1.3 THz Hot Electron Bolometer (HEB) receiver was installed for the atmospheric window 1250-1380 GHz. This instrument is part of a 4-channel receiver cryostat with the other channels being 211-275 GHz, 275-370 GHz and 380-500 GHz Sideband Separating (SSB) SIS receivers. This paper presents the first observations obtained so far with the 1.3 THz band during its first months of operation. The sky measurements were taken during opportunistic commissioning and science verification phases, when the weather conditions were sufficiently good with a Precipitable Water Vapor (PWV) below 0.25 mm, which was the case only a few nights during these months. We present the first observations of the molecular transition CO J=(11-10) line on different sources such as Orion-FIR4, CW-Leo and SgrB2(M). We describe the many challenges and difficulties encountered for achieving successful THz observations from a large sub-millimeter ground-based telescope. |
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619 |
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Rabanus, D.; Graf, U. U.; Philipp, M.; Ricken, O.; Stutzki, J.; Vowinkel, B.; Wiedner, M. C.; Walther, C.; Fischer, M.; Faist, J. |
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Phase locking of a 1.5 terahertz quantum cascade laser and use as a local oscillator in a heterodyne HEB receiver |
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2009 |
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Optics Express |
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17 |
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3 |
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1159-1168 |
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QCL heterodyne, 300 uW at 1.5 THz, HEB mixer |
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We demonstrate for the first time the closure of an electronic phase lock loop for a continuous–wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better than 100 Hz, limited by the resolution bandwidth of the spectrum analyser. The PLL electronics make use of the intermediate frequency (IF) obtained from a hot electron bolometer (HEB) which is downconverted to a PLL IF of 125 MHz. The coarse selection of the longitudinal mode and the fine tuning is achieved via the bias voltage of the QCL. Within a QCL cavity mode, the free-running QCL shows frequency fluctuations of about 5 MHz, which the PLL circuit is able to control via the Stark–shift of the QCL gain material. Temperature dependent tuning is shown to be nonlinear, and of the order of -16 MHz/K. Additionally we have used the QCL as local oscillator (LO) to pump an HEB and perform, again for the first time at 1.5 THz, a heterodyne experiment, and obtain a receiver noise temperature of 1741 K. |
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628 |
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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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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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Scheel, Stefan |
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Single-photon sources–an introduction |
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2009 |
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J. Modern Opt. |
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56 |
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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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669 |
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Karpowicz, Nicholas; Lu, Xiaofei; Zhang, X.-C. |
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Terahertz gas photonics |
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2009 |
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J. Modern Opt. |
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56 |
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10 |
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1137-1150 |
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The underlying physics of the generation and detection of terahertz (THz) waves in gases are described. The THz wave generation process takes place in two steps: asymmetric gas ionization by two-frequency laser fields, followed by interaction of the ionized electron wave packets with the surrounding medium, producing an intense ‘echo' with tunable spectral content. In order to clarify the physical picture at the moment of ionization, the laser–atom interaction is treated through solution of the time-dependent Schrödinger equation, yielding an ab initio understanding of the release of the electron wave packets. The second step, where the electrons interact with the surrounding plasma is treated analytically. The resulting pressure dependence of the THz radiation is explored in detail. The THz wave detection process is shown to be the result of four-wave mixing, leading to analytical expressions of the signal obtained which allow for improved optimization of systems that exploit these effects. |
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670 |
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Polyakov, Sergey V.; Migdalla, Alan L. |
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Quantum radiometry |
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2009 |
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J. Modern Opt. |
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56 |
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9 |
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1045-1052 |
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We review radiometric techniques that take advantage of photon counting and stem from the quantum laws of nature. We present a brief history of metrological experiments and review the current state of experimental quantum radiometry. |
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671 |
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Wang, Zhen; Miki, S.; Fujiwara, M. |
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Superconducting nanowire single-photon detectors for quantum information and communications |
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2009 |
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IEEE J. Sel. Topics Quantum Electron. |
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15 |
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6 |
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1741-1747 |
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SSPD |
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Superconducting nanowire single-photon detectors (SNSPDs or SSPD) are highly promising devices in the growing field of quantum information and communications technology. We have developed a practical SSPD system with our superconducting thin films and devices fabrication, optical coupling packaging, and cryogenic technology. The SSPD system consists of six-channel SSPD devices and a compact Gifford-McMahon (GM) cryocooler, and can operate continuously on 100 V ac power without the need for any cryogens. The SSPD devices were fabricated from high-quality niobium nitride (NbN) ultrathin films that were epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices were temperature stabilized to 2.96 K ± 10 mK. The system detection efficiency for an SSPD device with an area of 20 × 20 ¿m2 was found to be 2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count rate of 100 Hz, and a jitter of 100 ps full-width at half maximum. We also performed ultrafast BB84 quantum key distribution (QKD) field testing and entanglement-based QKD experiments using these SSPD devices. |
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Yang, J.K.W.; Kerman, A.J.; Dauler, E.A.; Cord, B.; Anant, V.; Molnar, R.J.; Berggren, K.K. |
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Suppressed critical current in superconducting nanowire single-photon detectors with high fill-factors |
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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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318-322 |
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SNSPD |
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In this work we present a new fabrication process that enabled the fabrication of superconducting nanowire single photon detectors SNSPD with fill-factors as high as 88% with gaps between nanowires as small as 12 nm. This fabrication process combined high-resolution electron-beam lithography with photolithography. Although this work was motivated by the potential of increased detection efficiency with higher fill-factor devices, test results showed an unexpected systematic suppression in device critical currents with increasing fill-factor. |
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