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| Author |
Baek, Burm; Lita, Adriana E.; Verma, Varun; Nam, Sae Woo |
| Title |
Superconducting a-WxSi1–x nanowire single-photon detector with saturated internal quantum efficiency from visible to 1850 nm |
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Journal Article |
| Year |
2011 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
98 |
Issue |
25 |
Pages |
3 |
| Keywords |
SNSPD |
Abstract  |
We have developed a single-photon detector based on superconducting amorphous tungsten–silicon alloy (a-WxSi1–x) nanowire. Our device made from a uniform a-WxSi1–x nanowire covers a practical detection area (16 μm×16 μm) and shows high sensitivity featuring a plateau of the internal quantum efficiencies, i.e., efficiencies of generating an electrical pulse per absorbed photon, over a broad wavelength and bias range. This material system for superconducting nanowire detector technology could overcome the limitations of the prevalent nanowire devices based on NbN and lead to more practical, ideal single-photon detectors having high efficiency, low noise, and high count rates. |
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RPLAB @ gujma @ |
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665 |
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Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M. |
| Title |
Quantum noise in a terahertz hot electron bolometer mixer |
Type |
Journal Article |
| Year |
2010 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
96 |
Issue |
11 |
Pages |
111113-(1-3) |
| Keywords |
HEB mixer, quantum limit, quantum noise, vacuum box, THz, Terahertz |
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We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The beta-factor (the quantum efficiency of the HEB) obtained experimentally agrees reasonably well with the calculated value. |
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Mannino, Giovanni; Spinella, Corrado; Ruggeri, Rosa; La Magna, Antonino; Fisicaro, Giuseppe; Fazio, Enza; Neri, Fortunato; Privitera, Vittorio |
| Title |
Crystallization of implanted amorphous silicon during millisecond annealing by infrared laser irradiation |
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Journal Article |
| Year |
2010 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
97 |
Issue |
2 |
Pages |
3 |
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Annealing |
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We investigated the homogenous nucleation of crystalline grains in amorphous Si during transient temperature pulse of few milliseconds IR laser irradiation. The crystallized volume fraction is ~80%. Significant crystallization occurs in nonsteady regime because of the rapid temperature variation (106 °C/s). Our model combines the time evolution of the crystal grain population with the consumption of the amorphous volume due to the growth of grains. Thanks to the experimental approach based on a laser source to heat α-Si and the theoretical model we extended the description of the spontaneous crystallization up to 1323 K or 250 K above the temperature investigated by conventional annealing. |
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Annealing |
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RPLAB @ gujma @ |
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691 |
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Sekine, Norihiko; Hosako, Iwao |
| Title |
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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Barends, R.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M. |
| Title |
Current-induced vortex unbinding in bolometer mixers |
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Journal Article |
| Year |
2005 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
87 |
Issue |
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Pages |
263506 (1 to 3) |
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HEB mixer numerical model, HEB model, IV-curves, vortex-antivortex, Berezinskii–Kosterlitz–Thouless theory, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model, self-heating effect, temperature profile |
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We present a description of the current-voltage characteristics of hot electron bolometers in terms of the current-dependent intrinsic resistive transition of NbN films. We find that, by including this current dependence, we can correctly predict the complete current-voltage characteristics, showing excellent agreement with measurements for both low and high bias and for small as well as large devices. It is assumed that the current dependence is due to vortex-antivortex unbinding as described in the Berezinskii–Kosterlitz–Thouless theory. The presented approach will be useful in guiding device optimization for noise and bandwidth. |
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