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Sekine, Norihiko; Hosako, Iwao |
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Title |
Intensity modulation of terahertz quantum cascade lasers under external light injection |
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2009 |
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Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
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95 |
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201106(1-3) |
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Keywords  |
QCL modulation, THz, terahertz |
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Abstract |
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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Kataoka, T; Kajikawa, K.; Kitagawa, J.; Kadoya, Y; Takemura, Y. |
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Title |
Improved sensitivity of terahertz detection by GaAs photoconductive antennas excited at 1560 nm |
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Journal Article |
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Year |
2010 |
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Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
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97 |
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201110 (1-3) |
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Keywords |
photoconductive antenna (PCA) |
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The terahertz detection by photoconductive antennas (PCAs) based on low-temperature grown (LTG) GaAs with 1.5 μm pulse excitation was revisited. We found that the detection efficiency can be improved by a factor of 10 (20 dB) by reducing the excitation spot size and the gap length of the PCA, maintaining the low noise feature of the PCA on LTG GaAs. As a result, the signal-to-noise ratio higher than 50 dB was obtained at a reasonable incident power of 9.5 mW, suggesting that the scheme is promising for the detection of terahertz waves in practical time domain systems. |
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904 |
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Sprengers, J. P.; Gaggero, A.; Sahin, D.; Jahanmirinejad, S.; Frucci, G.; Mattioli, F.; Leoni, R.; Beetz, J.; Lermer, M.; Kamp, M.; Höfling, S.; Sanjines, R.; Fiore A. |
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Waveguide superconducting single-photon detectors for integrated quantum photonic circuits |
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Journal Article |
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2011 |
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Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
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Volume |
99 |
Issue |
18 |
Pages |
181110(1-3) |
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Keywords |
optical waveguides, waveguide SSPD |
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The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (~0%) at telecom wavelengths, high timing accuracy (~0 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators. |
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847 |
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Il’in, K. S.; Milostnaya, I. I.; Verevkin, A. A.; Gol’tsman, G. N.; Gershenzon, E. M.; Sobolewski, R. |
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Title |
Ultimate quantum efficiency of a superconducting hot-electron photodetector |
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Year |
1998 |
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Appl. Phys. Lett. |
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Appl. Phys. Lett. |
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Volume |
73 |
Issue |
26 |
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3938-3940 |
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Keywords |
NbN SSPD, SNSPD |
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The quantum efficiency and current and voltage responsivities of fast hot-electron photodetectors, fabricated from superconducting NbN thin films and biased in the resistive state, have been shown to reach values of 340, 220 A/W, and 4×104 V/W,
respectively, for infrared radiation with a wavelength of 0.79 μm. The characteristics of the photodetectors are presented within the general model, based on relaxation processes in the nonequilibrium electron heating of a superconducting thin film. The observed, very high efficiency and sensitivity of the superconductor absorbing the photon are explained by the high multiplication rate of quasiparticles during the avalanche breaking of Cooper pairs. |
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0003-6951 |
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1579 |
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Kerman, A. J.; Dauler, E. A.; Keicher, W. E.; Yang, J. K. W.; Berggren, K. K.; Gol’tsman, G.; Voronov, B. |
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Title |
Kinetic-inductance-limited reset time of superconducting nanowire photon counters |
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2006 |
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Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
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Volume |
88 |
Issue |
11 |
Pages |
111116 (1 to 3) |
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Keywords |
NbN SSPD, SNSPD |
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We investigate the recovery of superconducting NbN-nanowire photon counters after detection of an optical pulse at a wavelength of 1550nm, and present a model that quantitatively accounts for our observations. The reset time is found to be limited by the large kinetic inductance of these nanowires, which forces a tradeoff between counting rate and either detection efficiency or active area. Devices of usable size and high detection efficiency are found to have reset times orders of magnitude longer than their intrinsic photoresponse time.
The authors acknowledge D. Oates and W. Oliver (MIT Lincoln Laboratory), S.W. Nam, A. Miller, and R. Hadfield (NIST) and R. Sobolewski, A. Pearlman, and A. Verevkin (University of Rochester) for helpful discussions and technical assistance. This work made use of MIT’s shared scanning-electron-beam-lithography facility in the Research Laboratory of Electronics. This work is sponsored by the United States Air Force under Air Force Contract No. FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the authors and are not necessarily endorsed by the United States Government. |
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0003-6951 |
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1453 |
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