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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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Baryshev A.; Hovenier J.N.; Adam A.J.L.; Kašalynas I.; Gao J.R.; Klaassen T.O.; Williams B.S.; Kumar S.; Hu Q.; Reno J.L. |
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Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser |
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Journal Article |
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2006 |
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Physics Letters |
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89 |
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We have studied the phase locking and spectral linewidth of an ~ 2.7 THz quantum cascade laser by mixing its two lateral lasing modes. The beat signal at about 8 GHz is compared with a microwave eference by applying conventional phase lock loop circuitry with feedback to the laser bias current. Phase locking has been demonstrated, resulting in a narrow beat linewidth of less than 10 Hz. Under requency stabilization we find that the terahertz line profile is essentially Lorentzian with a minimum linewidth of ~ 6.3 kHz. Power dependent measurements suggest that this linewidth does not approach the Schawlow-Townes limit. |
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RPLAB @ atomics90 @ |
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967 |
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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 |
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2010 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
| Volume |
97 |
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2 |
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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 |
| Year |
2009 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
95 |
Issue |
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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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